Split ConstellationMsg into ScriptMsg and CompositorMsg

29 files changed, 256 insertions, 207 deletions

diff --git a/components/compositing/compositor.rs b/components/compositing/compositor.rs
index 100967799fd..c251426dc48 100644
--- a/components/compositing/compositor.rs
+++ b/components/compositing/compositor.rs
@@ -28,7 +28,7 @@ use layers::scene::Scene;
 use layout_traits::LayoutControlChan;
 use msg::compositor_msg::{Epoch, EventResult, FrameTreeId, LayerId, LayerKind};
 use msg::compositor_msg::{LayerProperties, ScrollPolicy};
-use msg::constellation_msg::Msg as ConstellationMsg;
+use msg::constellation_msg::CompositorMsg as ConstellationMsg;
 use msg::constellation_msg::{AnimationState, Image, PixelFormat};
 use msg::constellation_msg::{ConstellationChan, Key, KeyModifiers, KeyState, LoadData};
 use msg::constellation_msg::{NavigationDirection, PipelineId, WindowSizeData};
@@ -168,7 +168,7 @@ pub struct IOCompositor<Window: WindowMethods> {
     frame_tree_id: FrameTreeId,
 
     /// The channel on which messages can be sent to the constellation.
-    constellation_chan: ConstellationChan,
+    constellation_chan: ConstellationChan<ConstellationMsg>,
 
     /// The channel on which messages can be sent to the time profiler.
     time_profiler_chan: time::ProfilerChan,
@@ -703,7 +703,7 @@ impl<Window: WindowMethods> IOCompositor<Window> {
     fn set_frame_tree(&mut self,
                       frame_tree: &SendableFrameTree,
                       response_chan: Sender<()>,
-                      new_constellation_chan: ConstellationChan) {
+                      new_constellation_chan: ConstellationChan<ConstellationMsg>) {
         response_chan.send(()).unwrap();
 
         // There are now no more pending iframes.
diff --git a/components/compositing/compositor_task.rs b/components/compositing/compositor_task.rs
index fe8d82e26aa..70c59132b6d 100644
--- a/components/compositing/compositor_task.rs
+++ b/components/compositing/compositor_task.rs
@@ -12,6 +12,7 @@ use layers::layers::{BufferRequest, LayerBufferSet};
 use layers::platform::surface::{NativeDisplay, NativeSurface};
 use msg::compositor_msg::{Epoch, EventResult, FrameTreeId, LayerId, LayerProperties};
 use msg::compositor_msg::{PaintListener, ScriptToCompositorMsg};
+use msg::constellation_msg::CompositorMsg as ConstellationMsg;
 use msg::constellation_msg::{AnimationState, ConstellationChan, PipelineId};
 use msg::constellation_msg::{Image, Key, KeyModifiers, KeyState};
 use profile_traits::mem;
@@ -179,7 +180,7 @@ pub enum Msg {
     /// Alerts the compositor that the given pipeline has changed whether it is running animations.
     ChangeRunningAnimationsState(PipelineId, AnimationState),
     /// Replaces the current frame tree, typically called during main frame navigation.
-    SetFrameTree(SendableFrameTree, Sender<()>, ConstellationChan),
+    SetFrameTree(SendableFrameTree, Sender<()>, ConstellationChan<ConstellationMsg>),
     /// The load of a page has begun: (can go back, can go forward).
     LoadStart(bool, bool),
     /// The load of a page has completed: (can go back, can go forward).
@@ -295,7 +296,7 @@ pub struct InitialCompositorState {
     /// A port on which messages inbound to the compositor can be received.
     pub receiver: Box<CompositorReceiver>,
     /// A channel to the constellation.
-    pub constellation_chan: ConstellationChan,
+    pub constellation_chan: ConstellationChan<ConstellationMsg>,
     /// A channel to the time profiler thread.
     pub time_profiler_chan: time::ProfilerChan,
     /// A channel to the memory profiler thread.
diff --git a/components/compositing/constellation.rs b/components/compositing/constellation.rs
index 92e6d768bdd..8d8d24d050a 100644
--- a/components/compositing/constellation.rs
+++ b/components/compositing/constellation.rs
@@ -14,7 +14,7 @@ use canvas::webgl_paint_task::WebGLPaintTask;
 use canvas_traits::CanvasMsg;
 use clipboard::ClipboardContext;
 use compositor_task::CompositorProxy;
-use compositor_task::Msg as CompositorMsg;
+use compositor_task::Msg as ToCompositorMsg;
 use devtools_traits::{ChromeToDevtoolsControlMsg, DevtoolsControlMsg};
 use euclid::scale_factor::ScaleFactor;
 use euclid::size::{Size2D, TypedSize2D};
@@ -23,7 +23,8 @@ use ipc_channel::ipc::{self, IpcSender};
 use layout_traits::{LayoutControlChan, LayoutTaskFactory};
 use msg::compositor_msg::Epoch;
 use msg::constellation_msg::AnimationState;
-use msg::constellation_msg::Msg as ConstellationMsg;
+use msg::constellation_msg::CompositorMsg as FromCompositorMsg;
+use msg::constellation_msg::ScriptMsg as FromScriptMsg;
 use msg::constellation_msg::WebDriverCommandMsg;
 use msg::constellation_msg::{FrameId, PipelineId};
 use msg::constellation_msg::{IframeLoadInfo, IFrameSandboxState, MozBrowserEvent, NavigationDirection};
@@ -75,16 +76,16 @@ enum ReadyToSave {
 /// the `script` crate).
 pub struct Constellation<LTF, STF> {
     /// A channel through which script messages can be sent to this object.
-    pub script_sender: ConstellationChan,
+    pub script_sender: ConstellationChan<FromScriptMsg>,
 
     /// A channel through which compositor messages can be sent to this object.
-    pub compositor_sender: ConstellationChan,
+    pub compositor_sender: ConstellationChan<FromCompositorMsg>,
 
     /// Receives messages from scripts.
-    pub script_receiver: Receiver<ConstellationMsg>,
+    pub script_receiver: Receiver<FromScriptMsg>,
 
     /// Receives messages from the compositor
-    pub compositor_receiver: Receiver<ConstellationMsg>,
+    pub compositor_receiver: Receiver<FromCompositorMsg>,
 
     /// A channel (the implementation of which is port-specific) through which messages can be sent
     /// to the compositor.
@@ -259,14 +260,13 @@ enum ExitPipelineMode {
 }
 
 impl<LTF: LayoutTaskFactory, STF: ScriptTaskFactory> Constellation<LTF, STF> {
-    pub fn start(state: InitialConstellationState) -> ConstellationChan {
-        let (script_receiver, script_sender) = ConstellationChan::new();
-        let (compositor_receiver, compositor_sender) = ConstellationChan::new();
-        let script_sender_clone = script_sender.clone();
+    pub fn start(state: InitialConstellationState) -> ConstellationChan<FromCompositorMsg> {
+        let (script_receiver, script_sender) = ConstellationChan::<FromScriptMsg>::new();
+        let (compositor_receiver, compositor_sender) = ConstellationChan::<FromCompositorMsg>::new();
         let compositor_sender_clone = compositor_sender.clone();
         spawn_named("Constellation".to_owned(), move || {
             let mut constellation: Constellation<LTF, STF> = Constellation {
-                script_sender: script_sender_clone,
+                script_sender: script_sender,
                 compositor_sender: compositor_sender_clone,
                 script_receiver: script_receiver,
                 compositor_receiver: compositor_receiver,
@@ -313,18 +313,9 @@ impl<LTF: LayoutTaskFactory, STF: ScriptTaskFactory> Constellation<LTF, STF> {
         compositor_sender
     }
 
-#[allow(unsafe_code)]
     fn run(&mut self) {
         loop {
-            let request = {
-                let receiver_from_script = &self.script_receiver;
-                let receiver_from_compositor = &self.compositor_receiver;
-                select! {
-                    msg = receiver_from_script.recv() => msg.unwrap(),
-                    msg = receiver_from_compositor.recv() => msg.unwrap()
-                }
-            };
-            if !self.handle_request(request) {
+            if !self.handle_request() {
                 break;
             }
         }
@@ -420,104 +411,155 @@ impl<LTF: LayoutTaskFactory, STF: ScriptTaskFactory> Constellation<LTF, STF> {
     }
 
     /// Handles loading pages, navigation, and granting access to the compositor
-    fn handle_request(&mut self, request: ConstellationMsg) -> bool {
+    #[allow(unsafe_code)]
+    fn handle_request(&mut self) -> bool {
+        enum Request {
+            Script(FromScriptMsg),
+            Compositor(FromCompositorMsg)
+        }
+
+        let request = {
+            let receiver_from_script = &self.script_receiver;
+            let receiver_from_compositor = &self.compositor_receiver;
+            select! {
+                msg = receiver_from_script.recv() =>
+                    Request::Script(msg.unwrap()),
+                msg = receiver_from_compositor.recv() =>
+                    Request::Compositor(msg.unwrap())
+            }
+        };
+
         match request {
-            ConstellationMsg::Exit => {
+            // Messages from compositor
+
+
+            Request::Compositor(FromCompositorMsg::Exit) => {
                 debug!("constellation exiting");
                 self.handle_exit();
                 return false;
             }
-            ConstellationMsg::Failure(Failure { pipeline_id, parent_info }) => {
-                self.handle_failure_msg(pipeline_id, parent_info);
+            // The compositor discovered the size of a subframe. This needs to be reflected by all
+            // frame trees in the navigation context containing the subframe.
+            Request::Compositor(FromCompositorMsg::FrameSize(pipeline_id, size)) => {
+                debug!("constellation got frame size message");
+                self.handle_frame_size_msg(pipeline_id, &Size2D::from_untyped(&size));
+            }
+            Request::Compositor(FromCompositorMsg::GetFrame(pipeline_id, resp_chan)) => {
+                debug!("constellation got get root pipeline message");
+                self.handle_get_frame(pipeline_id, resp_chan);
+            }
+            Request::Compositor(FromCompositorMsg::GetPipeline(frame_id, resp_chan)) => {
+                debug!("constellation got get root pipeline message");
+                self.handle_get_pipeline(frame_id, resp_chan);
+            }
+            Request::Compositor(FromCompositorMsg::GetPipelineTitle(pipeline_id)) => {
+                debug!("constellation got get-pipeline-title message");
+                self.handle_get_pipeline_title_msg(pipeline_id);
+            }
+            Request::Compositor(FromCompositorMsg::KeyEvent(key, state, modifiers)) => {
+                debug!("constellation got key event message");
+                self.handle_key_msg(key, state, modifiers);
+            }
+            // Load a new page from a typed url
+            // If there is already a pending page (self.pending_frames), it will not be overridden;
+            // However, if the id is not encompassed by another change, it will be.
+            Request::Compositor(FromCompositorMsg::LoadUrl(source_id, load_data)) => {
+                debug!("constellation got URL load message from compositor");
+                self.handle_load_url_msg(source_id, load_data);
+            }
+            Request::Compositor(FromCompositorMsg::IsReadyToSaveImage(pipeline_states)) => {
+                let is_ready = self.handle_is_ready_to_save_image(pipeline_states);
+                if opts::get().is_running_problem_test {
+                    println!("got ready to save image query, result is {:?}", is_ready);
+                }
+                let is_ready = is_ready == ReadyToSave::Ready;
+                self.compositor_proxy.send(ToCompositorMsg::IsReadyToSaveImageReply(is_ready));
+                if opts::get().is_running_problem_test {
+                    println!("sent response");
+                }
             }
             // This should only be called once per constellation, and only by the browser
-            ConstellationMsg::InitLoadUrl(url) => {
+            Request::Compositor(FromCompositorMsg::InitLoadUrl(url)) => {
                 debug!("constellation got init load URL message");
                 self.handle_init_load(url);
             }
-            // The compositor discovered the size of a subframe. This needs to be reflected by all
-            // frame trees in the navigation context containing the subframe.
-            ConstellationMsg::FrameSize(pipeline_id, size) => {
-                debug!("constellation got frame size message");
-                self.handle_frame_size_msg(pipeline_id, &Size2D::from_untyped(&size));
+            // Handle a forward or back request
+            Request::Compositor(FromCompositorMsg::Navigate(pipeline_info, direction)) => {
+                debug!("constellation got navigation message from compositor");
+                self.handle_navigate_msg(pipeline_info, direction);
+            }
+            Request::Compositor(FromCompositorMsg::ResizedWindow(new_size)) => {
+                debug!("constellation got window resize message");
+                self.handle_resized_window_msg(new_size);
+            }
+            Request::Compositor(FromCompositorMsg::TickAnimation(pipeline_id)) => {
+                self.handle_tick_animation(pipeline_id)
+            }
+            Request::Compositor(FromCompositorMsg::WebDriverCommand(command)) => {
+                debug!("constellation got webdriver command message");
+                self.handle_webdriver_msg(command);
+            }
+
+
+            // Messages from script
+
+
+            Request::Script(FromScriptMsg::Failure(Failure { pipeline_id, parent_info })) => {
+                self.handle_failure_msg(pipeline_id, parent_info);
             }
-            ConstellationMsg::ScriptLoadedURLInIFrame(load_info) => {
+            Request::Script(FromScriptMsg::ScriptLoadedURLInIFrame(load_info)) => {
                 debug!("constellation got iframe URL load message {:?} {:?} {:?}",
                        load_info.containing_pipeline_id,
                        load_info.old_subpage_id,
                        load_info.new_subpage_id);
                 self.handle_script_loaded_url_in_iframe_msg(load_info);
             }
-            ConstellationMsg::SetCursor(cursor) => {
+            Request::Script(FromScriptMsg::SetCursor(cursor)) => {
                 self.handle_set_cursor_msg(cursor)
             }
-            ConstellationMsg::ChangeRunningAnimationsState(pipeline_id, animation_state) => {
+            Request::Script(FromScriptMsg::ChangeRunningAnimationsState(pipeline_id, animation_state)) => {
                 self.handle_change_running_animations_state(pipeline_id, animation_state)
             }
-            ConstellationMsg::TickAnimation(pipeline_id) => {
-                self.handle_tick_animation(pipeline_id)
-            }
-            // Load a new page, usually -- but not always -- from a mouse click or typed url
+            // Load a new page from a mouse click
             // If there is already a pending page (self.pending_frames), it will not be overridden;
             // However, if the id is not encompassed by another change, it will be.
-            ConstellationMsg::LoadUrl(source_id, load_data) => {
-                debug!("constellation got URL load message");
+            Request::Script(FromScriptMsg::LoadUrl(source_id, load_data)) => {
+                debug!("constellation got URL load message from script");
                 self.handle_load_url_msg(source_id, load_data);
             }
-            // A page loaded through one of several methods above has completed all parsing,
-            // script, and reflow messages have been sent.
-            ConstellationMsg::LoadComplete(pipeline_id) => {
+            // A page loaded has completed all parsing, script, and reflow messages have been sent.
+            Request::Script(FromScriptMsg::LoadComplete(pipeline_id)) => {
                 debug!("constellation got load complete message");
                 self.handle_load_complete_msg(&pipeline_id)
             }
             // The DOM load event fired on a document
-            ConstellationMsg::DOMLoad(pipeline_id) => {
+            Request::Script(FromScriptMsg::DOMLoad(pipeline_id)) => {
                 debug!("constellation got dom load message");
                 self.handle_dom_load(pipeline_id)
             }
             // Handle a forward or back request
-            ConstellationMsg::Navigate(pipeline_info, direction) => {
-                debug!("constellation got navigation message");
+            Request::Script(FromScriptMsg::Navigate(pipeline_info, direction)) => {
+                debug!("constellation got navigation message from script");
                 self.handle_navigate_msg(pipeline_info, direction);
             }
             // Notification that painting has finished and is requesting permission to paint.
-            ConstellationMsg::PainterReady(pipeline_id) => {
+            Request::Script(FromScriptMsg::PainterReady(pipeline_id)) => {
                 debug!("constellation got painter ready message");
                 self.handle_painter_ready_msg(pipeline_id);
             }
-            ConstellationMsg::ResizedWindow(new_size) => {
-                debug!("constellation got window resize message");
-                self.handle_resized_window_msg(new_size);
-            }
-            ConstellationMsg::KeyEvent(key, state, modifiers) => {
-                debug!("constellation got key event message");
-                self.handle_key_msg(key, state, modifiers);
-            }
-            ConstellationMsg::GetPipelineTitle(pipeline_id) => {
-                debug!("constellation got get-pipeline-title message");
-                self.handle_get_pipeline_title_msg(pipeline_id);
-            }
-            ConstellationMsg::MozBrowserEvent(pipeline_id,
+            Request::Script(FromScriptMsg::MozBrowserEvent(pipeline_id,
                                               subpage_id,
-                                              event) => {
+                                              event)) => {
                 debug!("constellation got mozbrowser event message");
                 self.handle_mozbrowser_event_msg(pipeline_id,
                                                  subpage_id,
                                                  event);
             }
-            ConstellationMsg::GetPipeline(frame_id, resp_chan) => {
-                debug!("constellation got get root pipeline message");
-                self.handle_get_pipeline(frame_id, resp_chan);
-            }
-            ConstellationMsg::GetFrame(pipeline_id, resp_chan) => {
-                debug!("constellation got get root pipeline message");
-                self.handle_get_frame(pipeline_id, resp_chan);
-            }
-            ConstellationMsg::Focus(pipeline_id) => {
+            Request::Script(FromScriptMsg::Focus(pipeline_id)) => {
                 debug!("constellation got focus message");
                 self.handle_focus_msg(pipeline_id);
             }
-            ConstellationMsg::GetClipboardContents(sender) => {
+            Request::Script(FromScriptMsg::GetClipboardContents(sender)) => {
                 let result = self.clipboard_ctx.as_ref().map_or(
                     "".to_owned(),
                     |ctx| ctx.get_contents().unwrap_or_else(|e| {
@@ -527,55 +569,40 @@ impl<LTF: LayoutTaskFactory, STF: ScriptTaskFactory> Constellation<LTF, STF> {
                 );
                 sender.send(result).unwrap();
             }
-            ConstellationMsg::SetClipboardContents(s) => {
+            Request::Script(FromScriptMsg::SetClipboardContents(s)) => {
                 if let Some(ref mut ctx) = self.clipboard_ctx {
                     if let Err(e) = ctx.set_contents(s) {
                         debug!("Error setting clipboard contents ({})", e);
                     }
                 }
             }
-            ConstellationMsg::WebDriverCommand(command) => {
-                debug!("constellation got webdriver command message");
-                self.handle_webdriver_msg(command);
-            }
-            ConstellationMsg::ViewportConstrained(pipeline_id, constraints) => {
+            Request::Script(FromScriptMsg::ViewportConstrained(pipeline_id, constraints)) => {
                 debug!("constellation got viewport-constrained event message");
                 self.handle_viewport_constrained_msg(pipeline_id, constraints);
             }
-            ConstellationMsg::IsReadyToSaveImage(pipeline_states) => {
-                let is_ready = self.handle_is_ready_to_save_image(pipeline_states);
-                if opts::get().is_running_problem_test {
-                    println!("got ready to save image query, result is {:?}", is_ready);
-                }
-                let is_ready = is_ready == ReadyToSave::Ready;
-                self.compositor_proxy.send(CompositorMsg::IsReadyToSaveImageReply(is_ready));
-                if opts::get().is_running_problem_test {
-                    println!("sent response");
-                }
-            }
-            ConstellationMsg::RemoveIFrame(pipeline_id) => {
+            Request::Script(FromScriptMsg::RemoveIFrame(pipeline_id)) => {
                 debug!("constellation got remove iframe message");
                 self.handle_remove_iframe_msg(pipeline_id);
             }
-            ConstellationMsg::NewFavicon(url) => {
+            Request::Script(FromScriptMsg::NewFavicon(url)) => {
                 debug!("constellation got new favicon message");
-                self.compositor_proxy.send(CompositorMsg::NewFavicon(url));
+                self.compositor_proxy.send(ToCompositorMsg::NewFavicon(url));
             }
-            ConstellationMsg::HeadParsed => {
+            Request::Script(FromScriptMsg::HeadParsed) => {
                 debug!("constellation got head parsed message");
-                self.compositor_proxy.send(CompositorMsg::HeadParsed);
+                self.compositor_proxy.send(ToCompositorMsg::HeadParsed);
             }
-            ConstellationMsg::CreateCanvasPaintTask(size, sender) => {
+            Request::Script(FromScriptMsg::CreateCanvasPaintTask(size, sender)) => {
                 debug!("constellation got create-canvas-paint-task message");
                 self.handle_create_canvas_paint_task_msg(&size, sender)
             }
-            ConstellationMsg::CreateWebGLPaintTask(size, attributes, sender) => {
+            Request::Script(FromScriptMsg::CreateWebGLPaintTask(size, attributes, sender)) => {
                 debug!("constellation got create-WebGL-paint-task message");
                 self.handle_create_webgl_paint_task_msg(&size, attributes, sender)
             }
-            ConstellationMsg::NodeStatus(message) => {
+            Request::Script(FromScriptMsg::NodeStatus(message)) => {
                 debug!("constellation got NodeStatus message");
-                self.compositor_proxy.send(CompositorMsg::Status(message));
+                self.compositor_proxy.send(ToCompositorMsg::Status(message));
             }
         }
         true
@@ -593,7 +620,7 @@ impl<LTF: LayoutTaskFactory, STF: ScriptTaskFactory> Constellation<LTF, STF> {
         });
         self.storage_task.send(StorageTaskMsg::Exit).unwrap();
         self.font_cache_task.exit();
-        self.compositor_proxy.send(CompositorMsg::ShutdownComplete);
+        self.compositor_proxy.send(ToCompositorMsg::ShutdownComplete);
     }
 
     fn handle_failure_msg(&mut self,
@@ -643,7 +670,7 @@ impl<LTF: LayoutTaskFactory, STF: ScriptTaskFactory> Constellation<LTF, STF> {
         self.new_pipeline(root_pipeline_id, None, Some(window_size), None, LoadData::new(url.clone()));
         self.handle_load_start_msg(&root_pipeline_id);
         self.push_pending_frame(root_pipeline_id, None);
-        self.compositor_proxy.send(CompositorMsg::ChangePageUrl(root_pipeline_id, url));
+        self.compositor_proxy.send(ToCompositorMsg::ChangePageUrl(root_pipeline_id, url));
     }
 
     fn handle_frame_size_msg(&mut self,
@@ -719,13 +746,13 @@ impl<LTF: LayoutTaskFactory, STF: ScriptTaskFactory> Constellation<LTF, STF> {
     }
 
     fn handle_set_cursor_msg(&mut self, cursor: Cursor) {
-        self.compositor_proxy.send(CompositorMsg::SetCursor(cursor))
+        self.compositor_proxy.send(ToCompositorMsg::SetCursor(cursor))
     }
 
     fn handle_change_running_animations_state(&mut self,
                                               pipeline_id: PipelineId,
                                               animation_state: AnimationState) {
-        self.compositor_proxy.send(CompositorMsg::ChangeRunningAnimationsState(pipeline_id,
+        self.compositor_proxy.send(ToCompositorMsg::ChangeRunningAnimationsState(pipeline_id,
                                                                                animation_state))
     }
 
@@ -789,7 +816,7 @@ impl<LTF: LayoutTaskFactory, STF: ScriptTaskFactory> Constellation<LTF, STF> {
         if let Some(id) = self.pipeline_to_frame_map.get(pipeline_id) {
             let forward = !self.frame(*id).next.is_empty();
             let back = !self.frame(*id).prev.is_empty();
-            self.compositor_proxy.send(CompositorMsg::LoadStart(back, forward));
+            self.compositor_proxy.send(ToCompositorMsg::LoadStart(back, forward));
         }
     }
 
@@ -804,7 +831,7 @@ impl<LTF: LayoutTaskFactory, STF: ScriptTaskFactory> Constellation<LTF, STF> {
 
         let forward = !self.frame(frame_id).next.is_empty();
         let back = !self.frame(frame_id).prev.is_empty();
-        self.compositor_proxy.send(CompositorMsg::LoadComplete(back, forward));
+        self.compositor_proxy.send(ToCompositorMsg::LoadComplete(back, forward));
     }
 
     fn handle_dom_load(&mut self,
@@ -920,7 +947,7 @@ impl<LTF: LayoutTaskFactory, STF: ScriptTaskFactory> Constellation<LTF, STF> {
                     ConstellationControlMsg::SendEvent(pipeline.id, event)).unwrap();
             }
             None => {
-                let event = CompositorMsg::KeyEvent(key, state, mods);
+                let event = ToCompositorMsg::KeyEvent(key, state, mods);
                 self.compositor_proxy.clone_compositor_proxy().send(event);
             }
         }
@@ -928,7 +955,7 @@ impl<LTF: LayoutTaskFactory, STF: ScriptTaskFactory> Constellation<LTF, STF> {
 
     fn handle_get_pipeline_title_msg(&mut self, pipeline_id: PipelineId) {
         match self.pipelines.get(&pipeline_id) {
-            None => self.compositor_proxy.send(CompositorMsg::ChangePageTitle(pipeline_id, None)),
+            None => self.compositor_proxy.send(ToCompositorMsg::ChangePageTitle(pipeline_id, None)),
             Some(pipeline) => {
                 pipeline.script_chan.send(ConstellationControlMsg::GetTitle(pipeline_id)).unwrap();
             }
@@ -1062,7 +1089,7 @@ impl<LTF: LayoutTaskFactory, STF: ScriptTaskFactory> Constellation<LTF, STF> {
                     frame.current
                 });
                 if Some(pipeline_id) == current_pipeline_id {
-                    self.compositor_proxy.send(CompositorMsg::CreatePng(reply));
+                    self.compositor_proxy.send(ToCompositorMsg::CreatePng(reply));
                 } else {
                     reply.send(None).unwrap();
                 }
@@ -1223,7 +1250,7 @@ impl<LTF: LayoutTaskFactory, STF: ScriptTaskFactory> Constellation<LTF, STF> {
     fn handle_viewport_constrained_msg(&mut self,
                                        pipeline_id: PipelineId,
                                        constraints: ViewportConstraints) {
-        self.compositor_proxy.send(CompositorMsg::ViewportConstrained(pipeline_id, constraints));
+        self.compositor_proxy.send(ToCompositorMsg::ViewportConstrained(pipeline_id, constraints));
     }
 
     /// Checks the state of all script and layout pipelines to see if they are idle
@@ -1419,7 +1446,7 @@ impl<LTF: LayoutTaskFactory, STF: ScriptTaskFactory> Constellation<LTF, STF> {
             let frame_tree = self.frame_to_sendable(root_frame_id);
 
             let (chan, port) = channel();
-            self.compositor_proxy.send(CompositorMsg::SetFrameTree(frame_tree,
+            self.compositor_proxy.send(ToCompositorMsg::SetFrameTree(frame_tree,
                                                                    chan,
                                                                    self.compositor_sender.clone()));
             if port.recv().is_err() {
diff --git a/components/compositing/headless.rs b/components/compositing/headless.rs
index 1db4d7b7ad5..52435af0cd7 100644
--- a/components/compositing/headless.rs
+++ b/components/compositing/headless.rs
@@ -7,7 +7,7 @@ use compositor_task::{InitialCompositorState, Msg};
 use euclid::scale_factor::ScaleFactor;
 use euclid::{Point2D, Size2D};
 use msg::constellation_msg::AnimationState;
-use msg::constellation_msg::Msg as ConstellationMsg;
+use msg::constellation_msg::CompositorMsg as ConstellationMsg;
 use msg::constellation_msg::{ConstellationChan, WindowSizeData};
 use profile_traits::mem;
 use profile_traits::time;
@@ -22,7 +22,7 @@ pub struct NullCompositor {
     /// The port on which we receive messages.
     pub port: Box<CompositorReceiver>,
     /// A channel to the constellation.
-    constellation_chan: ConstellationChan,
+    constellation_chan: ConstellationChan<ConstellationMsg>,
     /// A channel to the time profiler.
     time_profiler_chan: time::ProfilerChan,
     /// A channel to the memory profiler.
diff --git a/components/compositing/pipeline.rs b/components/compositing/pipeline.rs
index febd879768e..8742898eaa4 100644
--- a/components/compositing/pipeline.rs
+++ b/components/compositing/pipeline.rs
@@ -14,6 +14,7 @@ use ipc_channel::ipc::{self, IpcReceiver, IpcSender};
 use ipc_channel::router::ROUTER;
 use layers::geometry::DevicePixel;
 use layout_traits::{LayoutControlChan, LayoutTaskFactory};
+use msg::constellation_msg::ScriptMsg as ConstellationMsg;
 use msg::constellation_msg::{ConstellationChan, Failure, FrameId, PipelineId, SubpageId};
 use msg::constellation_msg::{LoadData, MozBrowserEvent, WindowSizeData};
 use msg::constellation_msg::{PipelineNamespaceId};
@@ -78,7 +79,7 @@ pub struct InitialPipelineState {
     /// If `None`, this is the root.
     pub parent_info: Option<(PipelineId, SubpageId)>,
     /// A channel to the associated constellation.
-    pub constellation_chan: ConstellationChan,
+    pub constellation_chan: ConstellationChan<ConstellationMsg>,
     /// A channel to schedule timer events.
     pub scheduler_chan: IpcSender<TimerEventRequest>,
     /// A channel to the compositor.
@@ -317,7 +318,7 @@ impl Pipeline {
 pub struct PipelineContent {
     id: PipelineId,
     parent_info: Option<(PipelineId, SubpageId)>,
-    constellation_chan: ConstellationChan,
+    constellation_chan: ConstellationChan<ConstellationMsg>,
     scheduler_chan: IpcSender<TimerEventRequest>,
     compositor_proxy: Box<CompositorProxy + Send + 'static>,
     devtools_chan: Option<IpcSender<ScriptToDevtoolsControlMsg>>,
diff --git a/components/gfx/paint_task.rs b/components/gfx/paint_task.rs
index a44e1bd4d54..82b0e75d284 100644
--- a/components/gfx/paint_task.rs
+++ b/components/gfx/paint_task.rs
@@ -21,7 +21,7 @@ use layers::layers::{BufferRequest, LayerBuffer, LayerBufferSet};
 use layers::platform::surface::{NativeDisplay, NativeSurface};
 use msg::compositor_msg::{Epoch, FrameTreeId, LayerId, LayerKind, LayerProperties};
 use msg::compositor_msg::{PaintListener, ScrollPolicy};
-use msg::constellation_msg::Msg as ConstellationMsg;
+use msg::constellation_msg::ScriptMsg as ConstellationMsg;
 use msg::constellation_msg::{ConstellationChan, Failure, PipelineId};
 use paint_context::PaintContext;
 use profile_traits::mem::{self, ReportsChan};
@@ -214,7 +214,7 @@ pub struct PaintTask<C> {
     layout_to_paint_port: Receiver<LayoutToPaintMsg>,
     chrome_to_paint_port: Receiver<ChromeToPaintMsg>,
     compositor: C,
-    constellation_chan: ConstellationChan,
+    constellation_chan: ConstellationChan<ConstellationMsg>,
 
     /// A channel to the time profiler.
     time_profiler_chan: time::ProfilerChan,
@@ -250,7 +250,7 @@ impl<C> PaintTask<C> where C: PaintListener + Send + 'static {
                   layout_to_paint_port: Receiver<LayoutToPaintMsg>,
                   chrome_to_paint_port: Receiver<ChromeToPaintMsg>,
                   compositor: C,
-                  constellation_chan: ConstellationChan,
+                  constellation_chan: ConstellationChan<ConstellationMsg>,
                   font_cache_task: FontCacheTask,
                   failure_msg: Failure,
                   time_profiler_chan: time::ProfilerChan,
@@ -268,7 +268,6 @@ impl<C> PaintTask<C> where C: PaintListener + Send + 'static {
                                                               font_cache_task,
                                                               time_profiler_chan.clone());
 
-                // FIXME: rust/#5967
                 let mut paint_task = PaintTask {
                     id: id,
                     _url: url,
diff --git a/components/layout/animation.rs b/components/layout/animation.rs
index 84b7a30479f..f3e01c20b8c 100644
--- a/components/layout/animation.rs
+++ b/components/layout/animation.rs
@@ -8,7 +8,8 @@ use clock_ticks;
 use flow::{self, Flow};
 use gfx::display_list::OpaqueNode;
 use incremental::{self, RestyleDamage};
-use msg::constellation_msg::{AnimationState, ConstellationChan, Msg, PipelineId};
+use msg::constellation_msg::ScriptMsg as ConstellationMsg;
+use msg::constellation_msg::{AnimationState, ConstellationChan, PipelineId};
 use script::layout_interface::Animation;
 use std::collections::HashMap;
 use std::collections::hash_map::Entry;
@@ -48,7 +49,7 @@ pub fn start_transitions_if_applicable(new_animations_sender: &Mutex<Sender<Anim
 
 /// Processes any new animations that were discovered after style recalculation.
 /// Also expire any old animations that have completed.
-pub fn update_animation_state(constellation_chan: &ConstellationChan,
+pub fn update_animation_state(constellation_chan: &ConstellationChan<ConstellationMsg>,
                               running_animations: &mut Arc<HashMap<OpaqueNode, Vec<Animation>>>,
                               new_animations_receiver: &Receiver<Animation>,
                               pipeline_id: PipelineId) {
@@ -100,7 +101,7 @@ pub fn update_animation_state(constellation_chan: &ConstellationChan,
     }
 
     constellation_chan.0
-                      .send(Msg::ChangeRunningAnimationsState(pipeline_id, animation_state))
+                      .send(ConstellationMsg::ChangeRunningAnimationsState(pipeline_id, animation_state))
                       .unwrap();
 }
 
diff --git a/components/layout/layout_task.rs b/components/layout/layout_task.rs
index 7975dd08685..0aed4e6c9c0 100644
--- a/components/layout/layout_task.rs
+++ b/components/layout/layout_task.rs
@@ -37,7 +37,7 @@ use layout_debug;
 use layout_traits::LayoutTaskFactory;
 use log;
 use msg::compositor_msg::{Epoch, LayerId, ScrollPolicy};
-use msg::constellation_msg::Msg as ConstellationMsg;
+use msg::constellation_msg::ScriptMsg as ConstellationMsg;
 use msg::constellation_msg::{ConstellationChan, Failure, PipelineId};
 use net_traits::image_cache_task::{ImageCacheChan, ImageCacheResult, ImageCacheTask};
 use opaque_node::OpaqueNodeMethods;
@@ -95,7 +95,7 @@ const DISPLAY_PORT_THRESHOLD_SIZE_FACTOR: i32 = 4;
 /// This needs to be protected by a mutex so we can do fast RPCs.
 pub struct LayoutTaskData {
     /// The channel on which messages can be sent to the constellation.
-    pub constellation_chan: ConstellationChan,
+    pub constellation_chan: ConstellationChan<ConstellationMsg>,
 
     /// The root stacking context.
     pub stacking_context: Option<Arc<StackingContext>>,
@@ -149,7 +149,7 @@ pub struct LayoutTask {
     font_cache_sender: Sender<()>,
 
     /// The channel on which messages can be sent to the constellation.
-    constellation_chan: ConstellationChan,
+    constellation_chan: ConstellationChan<ConstellationMsg>,
 
     /// The channel on which messages can be sent to the script task.
     script_chan: Sender<ConstellationControlMsg>,
@@ -226,7 +226,7 @@ impl LayoutTaskFactory for LayoutTask {
               is_iframe: bool,
               chan: OpaqueScriptLayoutChannel,
               pipeline_port: IpcReceiver<LayoutControlMsg>,
-              constellation_chan: ConstellationChan,
+              constellation_chan: ConstellationChan<ConstellationMsg>,
               failure_msg: Failure,
               script_chan: Sender<ConstellationControlMsg>,
               paint_chan: OptionalIpcSender<LayoutToPaintMsg>,
@@ -354,7 +354,7 @@ impl LayoutTask {
            is_iframe: bool,
            port: Receiver<Msg>,
            pipeline_port: IpcReceiver<LayoutControlMsg>,
-           constellation_chan: ConstellationChan,
+           constellation_chan: ConstellationChan<ConstellationMsg>,
            script_chan: Sender<ConstellationControlMsg>,
            paint_chan: OptionalIpcSender<LayoutToPaintMsg>,
            image_cache_task: ImageCacheTask,
diff --git a/components/layout/query.rs b/components/layout/query.rs
index 9057ac91967..c1aa95859c9 100644
--- a/components/layout/query.rs
+++ b/components/layout/query.rs
@@ -12,7 +12,7 @@ use fragment::{Fragment, FragmentBorderBoxIterator};
 use gfx::display_list::{DisplayItemMetadata, OpaqueNode};
 use layout_task::LayoutTaskData;
 use msg::constellation_msg::ConstellationChan;
-use msg::constellation_msg::Msg as ConstellationMsg;
+use msg::constellation_msg::ScriptMsg as ConstellationMsg;
 use opaque_node::OpaqueNodeMethods;
 use script::layout_interface::{ContentBoxResponse, ContentBoxesResponse, NodeGeometryResponse};
 use script::layout_interface::{HitTestResponse, LayoutRPC, MouseOverResponse, OffsetParentResponse};
diff --git a/components/layout_traits/lib.rs b/components/layout_traits/lib.rs
index 025713894e2..9205d420583 100644
--- a/components/layout_traits/lib.rs
+++ b/components/layout_traits/lib.rs
@@ -24,6 +24,7 @@ extern crate util;
 use gfx::font_cache_task::FontCacheTask;
 use gfx::paint_task::LayoutToPaintMsg;
 use ipc_channel::ipc::{IpcReceiver, IpcSender};
+use msg::constellation_msg::ScriptMsg as ConstellationMsg;
 use msg::constellation_msg::{ConstellationChan, Failure, PipelineId};
 use net_traits::image_cache_task::ImageCacheTask;
 use profile_traits::{mem, time};
@@ -46,7 +47,7 @@ pub trait LayoutTaskFactory {
               is_iframe: bool,
               chan: OpaqueScriptLayoutChannel,
               pipeline_port: IpcReceiver<LayoutControlMsg>,
-              constellation_chan: ConstellationChan,
+              constellation_chan: ConstellationChan<ConstellationMsg>,
               failure_msg: Failure,
               script_chan: Sender<ConstellationControlMsg>,
               layout_to_paint_chan: OptionalIpcSender<LayoutToPaintMsg>,
diff --git a/components/msg/constellation_msg.rs b/components/msg/constellation_msg.rs
index 7487fede8c2..59da1f175db 100644
--- a/components/msg/constellation_msg.rs
+++ b/components/msg/constellation_msg.rs
@@ -25,16 +25,21 @@ use util::geometry::{PagePx, ViewportPx};
 use util::mem::HeapSizeOf;
 use webdriver_msg::{LoadStatus, WebDriverScriptCommand};
 
-#[derive(Clone)]
-pub struct ConstellationChan(pub Sender<Msg>);
+pub struct ConstellationChan<T>(pub Sender<T>);
 
-impl ConstellationChan {
-    pub fn new() -> (Receiver<Msg>, ConstellationChan) {
+impl<T> ConstellationChan<T> {
+    pub fn new() -> (Receiver<T>, ConstellationChan<T>) {
         let (chan, port) = channel();
         (port, ConstellationChan(chan))
     }
 }
 
+impl<T> Clone for ConstellationChan<T> {
+    fn clone(&self) -> ConstellationChan<T> {
+        ConstellationChan(self.0.clone())
+    }
+}
+
 #[derive(PartialEq, Eq, Copy, Clone, Debug, Deserialize, Serialize)]
 pub enum IFrameSandboxState {
     IFrameSandboxed,
@@ -229,57 +234,38 @@ pub struct IframeLoadInfo {
     pub sandbox: IFrameSandboxState,
 }
 
-/// Messages from the compositor and script to the constellation.
+/// Messages from the compositor to the constellation.
 #[derive(Deserialize, Serialize)]
-pub enum Msg {
+pub enum CompositorMsg {
     Exit,
-    Failure(Failure),
-    InitLoadUrl(Url),
-    LoadComplete(PipelineId),
-    /// Dispatched after the DOM load event has fired on a document
-    DOMLoad(PipelineId),
     FrameSize(PipelineId, Size2D<f32>),
-    LoadUrl(PipelineId, LoadData),
-    ScriptLoadedURLInIFrame(IframeLoadInfo),
-    Navigate(Option<(PipelineId, SubpageId)>, NavigationDirection),
-    PainterReady(PipelineId),
-    ResizedWindow(WindowSizeData),
-    KeyEvent(Key, KeyState, KeyModifiers),
+    /// Request that the constellation send the FrameId corresponding to the document
+    /// with the provided pipeline id
+    GetFrame(PipelineId, IpcSender<Option<FrameId>>),
+    /// Request that the constellation send the current pipeline id for the provided frame
+    /// id, or for the root frame if this is None, over a provided channel
+    GetPipeline(Option<FrameId>, IpcSender<Option<PipelineId>>),
     /// Requests that the constellation inform the compositor of the title of the pipeline
     /// immediately.
     GetPipelineTitle(PipelineId),
-    /// Requests that the constellation inform the compositor of the a cursor change.
-    SetCursor(Cursor),
-    /// Dispatch a mozbrowser event to a given iframe. Only available in experimental mode.
-    MozBrowserEvent(PipelineId, SubpageId, MozBrowserEvent),
-    /// Indicates whether this pipeline is currently running animations.
-    ChangeRunningAnimationsState(PipelineId, AnimationState),
+    InitLoadUrl(Url),
+    /// Query the constellation to see if the current compositor output is stable
+    IsReadyToSaveImage(HashMap<PipelineId, Epoch>),
+    KeyEvent(Key, KeyState, KeyModifiers),
+    LoadUrl(PipelineId, LoadData),
+    Navigate(Option<(PipelineId, SubpageId)>, NavigationDirection),
+    ResizedWindow(WindowSizeData),
     /// Requests that the constellation instruct layout to begin a new tick of the animation.
     TickAnimation(PipelineId),
-    /// Request that the constellation send the current pipeline id for the provided frame
-    /// id, or for the root frame if this is None, over a provided channel
-    GetPipeline(Option<FrameId>, IpcSender<Option<PipelineId>>),
-    /// Request that the constellation send the FrameId corresponding to the document
-    /// with the provided pipeline id
-    GetFrame(PipelineId, IpcSender<Option<FrameId>>),
-    /// Notifies the constellation that this frame has received focus.
-    Focus(PipelineId),
-    /// Requests that the constellation retrieve the current contents of the clipboard
-    GetClipboardContents(IpcSender<String>),
-    /// Requests that the constellation set the contents of the clipboard
-    SetClipboardContents(String),
     /// Dispatch a webdriver command
     WebDriverCommand(WebDriverCommandMsg),
-    /// Notifies the constellation that the viewport has been constrained in some manner
-    ViewportConstrained(PipelineId, ViewportConstraints),
-    /// Query the constellation to see if the current compositor output is stable
-    IsReadyToSaveImage(HashMap<PipelineId, Epoch>),
-    /// Notification that this iframe should be removed.
-    RemoveIFrame(PipelineId),
-    /// Favicon detected
-    NewFavicon(Url),
-    /// <head> tag finished parsing
-    HeadParsed,
+}
+
+/// Messages from the script to the constellation.
+#[derive(Deserialize, Serialize)]
+pub enum ScriptMsg {
+    /// Indicates whether this pipeline is currently running animations.
+    ChangeRunningAnimationsState(PipelineId, AnimationState),
     /// Requests that a new 2D canvas thread be created. (This is done in the constellation because
     /// 2D canvases may use the GPU and we don't want to give untrusted content access to the GPU.)
     CreateCanvasPaintTask(Size2D<i32>, IpcSender<(IpcSender<CanvasMsg>, usize)>),
@@ -288,8 +274,34 @@ pub enum Msg {
     CreateWebGLPaintTask(Size2D<i32>,
                          GLContextAttributes,
                          IpcSender<Result<(IpcSender<CanvasMsg>, usize), String>>),
+    /// Dispatched after the DOM load event has fired on a document
+    DOMLoad(PipelineId),
+    Failure(Failure),
+    /// Notifies the constellation that this frame has received focus.
+    Focus(PipelineId),
+    /// Requests that the constellation retrieve the current contents of the clipboard
+    GetClipboardContents(IpcSender<String>),
+    /// <head> tag finished parsing
+    HeadParsed,
+    LoadComplete(PipelineId),
+    LoadUrl(PipelineId, LoadData),
+    /// Dispatch a mozbrowser event to a given iframe. Only available in experimental mode.
+    MozBrowserEvent(PipelineId, SubpageId, MozBrowserEvent),
+    Navigate(Option<(PipelineId, SubpageId)>, NavigationDirection),
+    /// Favicon detected
+    NewFavicon(Url),
     /// Status message to be displayed in the chrome, eg. a link URL on mouseover.
     NodeStatus(Option<String>),
+    PainterReady(PipelineId),
+    /// Notification that this iframe should be removed.
+    RemoveIFrame(PipelineId),
+    ScriptLoadedURLInIFrame(IframeLoadInfo),
+    /// Requests that the constellation set the contents of the clipboard
+    SetClipboardContents(String),
+    /// Requests that the constellation inform the compositor of the a cursor change.
+    SetCursor(Cursor),
+    /// Notifies the constellation that the viewport has been constrained in some manner
+    ViewportConstrained(PipelineId, ViewportConstraints),
 }
 
 #[derive(Clone, Eq, PartialEq, Deserialize, Serialize, Debug)]
diff --git a/components/script/clipboard_provider.rs b/components/script/clipboard_provider.rs
index 81860f59eef..9038f0ed393 100644
--- a/components/script/clipboard_provider.rs
+++ b/components/script/clipboard_provider.rs
@@ -4,7 +4,7 @@
 
 use ipc_channel::ipc;
 use msg::constellation_msg::ConstellationChan;
-use msg::constellation_msg::Msg as ConstellationMsg;
+use msg::constellation_msg::ScriptMsg as ConstellationMsg;
 use std::borrow::ToOwned;
 use std::sync::mpsc::channel;
 
@@ -15,7 +15,7 @@ pub trait ClipboardProvider {
     fn set_clipboard_contents(&mut self, String);
 }
 
-impl ClipboardProvider for ConstellationChan {
+impl ClipboardProvider for ConstellationChan<ConstellationMsg> {
     fn clipboard_contents(&mut self) -> String {
         let (tx, rx) = ipc::channel().unwrap();
         self.0.send(ConstellationMsg::GetClipboardContents(tx)).unwrap();
diff --git a/components/script/dom/bindings/global.rs b/components/script/dom/bindings/global.rs
index f3ae21e3212..da8d3dce87a 100644
--- a/components/script/dom/bindings/global.rs
+++ b/components/script/dom/bindings/global.rs
@@ -18,6 +18,7 @@ use ipc_channel::ipc::IpcSender;
 use js::jsapi::{GetGlobalForObjectCrossCompartment};
 use js::jsapi::{JSContext, JSObject, JS_GetClass, MutableHandleValue};
 use js::{JSCLASS_IS_DOMJSCLASS, JSCLASS_IS_GLOBAL};
+use msg::constellation_msg::ScriptMsg as ConstellationMsg;
 use msg::constellation_msg::{ConstellationChan, PipelineId, WorkerId};
 use net_traits::ResourceTask;
 use profile_traits::mem;
@@ -91,7 +92,7 @@ impl<'a> GlobalRef<'a> {
     }
 
     /// Get a `ConstellationChan` to send messages to the constellation channel when available.
-    pub fn constellation_chan(&self) -> ConstellationChan {
+    pub fn constellation_chan(&self) -> ConstellationChan<ConstellationMsg> {
         match *self {
             GlobalRef::Window(window) => window.constellation_chan(),
             GlobalRef::Worker(worker) => worker.constellation_chan(),
diff --git a/components/script/dom/bindings/trace.rs b/components/script/dom/bindings/trace.rs
index e05670b9a6d..9218919720f 100644
--- a/components/script/dom/bindings/trace.rs
+++ b/components/script/dom/bindings/trace.rs
@@ -54,6 +54,7 @@ use js::rust::Runtime;
 use layout_interface::{LayoutChan, LayoutRPC};
 use libc;
 use msg::constellation_msg::ConstellationChan;
+use msg::constellation_msg::ScriptMsg as ConstellationMsg;
 use msg::constellation_msg::{PipelineId, SubpageId, WindowSizeData, WorkerId};
 use net_traits::Metadata;
 use net_traits::image::base::Image;
@@ -271,7 +272,7 @@ no_jsmanaged_fields!(WorkerId);
 no_jsmanaged_fields!(QuirksMode);
 no_jsmanaged_fields!(Runtime);
 no_jsmanaged_fields!(Headers, Method);
-no_jsmanaged_fields!(ConstellationChan);
+no_jsmanaged_fields!(ConstellationChan<ConstellationMsg>);
 no_jsmanaged_fields!(LayoutChan);
 no_jsmanaged_fields!(WindowProxyHandler);
 no_jsmanaged_fields!(UntrustedNodeAddress);
diff --git a/components/script/dom/canvasrenderingcontext2d.rs b/components/script/dom/canvasrenderingcontext2d.rs
index 757f7e19cad..3cffea0f8c3 100644
--- a/components/script/dom/canvasrenderingcontext2d.rs
+++ b/components/script/dom/canvasrenderingcontext2d.rs
@@ -33,7 +33,7 @@ use euclid::point::Point2D;
 use euclid::rect::Rect;
 use euclid::size::Size2D;
 use ipc_channel::ipc::{self, IpcSender};
-use msg::constellation_msg::Msg as ConstellationMsg;
+use msg::constellation_msg::ScriptMsg as ConstellationMsg;
 use net_traits::image::base::PixelFormat;
 use net_traits::image_cache_task::ImageResponse;
 use num::{Float, ToPrimitive};
diff --git a/components/script/dom/document.rs b/components/script/dom/document.rs
index 1b8b99d90ec..108b68d9722 100644
--- a/components/script/dom/document.rs
+++ b/components/script/dom/document.rs
@@ -80,7 +80,7 @@ use layout_interface::{LayoutChan, Msg};
 use layout_interface::{ReflowGoal, ReflowQueryType};
 use msg::compositor_msg::ScriptToCompositorMsg;
 use msg::constellation_msg::AnimationState;
-use msg::constellation_msg::Msg as ConstellationMsg;
+use msg::constellation_msg::ScriptMsg as ConstellationMsg;
 use msg::constellation_msg::{ALT, CONTROL, SHIFT, SUPER};
 use msg::constellation_msg::{ConstellationChan, FocusType, Key, KeyModifiers, KeyState, MozBrowserEvent, SubpageId};
 use net_traits::ControlMsg::{GetCookiesForUrl, SetCookiesForUrl};
diff --git a/components/script/dom/htmlbodyelement.rs b/components/script/dom/htmlbodyelement.rs
index b7af752fdfc..32efe1bd53b 100644
--- a/components/script/dom/htmlbodyelement.rs
+++ b/components/script/dom/htmlbodyelement.rs
@@ -18,7 +18,7 @@ use dom::htmlelement::HTMLElement;
 use dom::node::{Node, document_from_node, window_from_node};
 use dom::virtualmethods::VirtualMethods;
 use msg::constellation_msg::ConstellationChan;
-use msg::constellation_msg::Msg as ConstellationMsg;
+use msg::constellation_msg::ScriptMsg as ConstellationMsg;
 use std::rc::Rc;
 use string_cache::Atom;
 use time;
diff --git a/components/script/dom/htmliframeelement.rs b/components/script/dom/htmliframeelement.rs
index edb45fbb14b..b3e62ef434b 100644
--- a/components/script/dom/htmliframeelement.rs
+++ b/components/script/dom/htmliframeelement.rs
@@ -25,7 +25,7 @@ use dom::window::Window;
 use js::jsapi::{JSAutoCompartment, JSAutoRequest, RootedValue, JSContext, MutableHandleValue};
 use js::jsval::{UndefinedValue, NullValue};
 use msg::constellation_msg::IFrameSandboxState::{IFrameSandboxed, IFrameUnsandboxed};
-use msg::constellation_msg::Msg as ConstellationMsg;
+use msg::constellation_msg::ScriptMsg as ConstellationMsg;
 use msg::constellation_msg::{ConstellationChan, IframeLoadInfo, MozBrowserEvent};
 use msg::constellation_msg::{NavigationDirection, PipelineId, SubpageId};
 use page::IterablePage;
diff --git a/components/script/dom/htmlinputelement.rs b/components/script/dom/htmlinputelement.rs
index 8b638236818..35b9d3cd4e7 100644
--- a/components/script/dom/htmlinputelement.rs
+++ b/components/script/dom/htmlinputelement.rs
@@ -28,6 +28,7 @@ use dom::node::{document_from_node, window_from_node};
 use dom::nodelist::NodeList;
 use dom::virtualmethods::VirtualMethods;
 use msg::constellation_msg::ConstellationChan;
+use msg::constellation_msg::ScriptMsg as ConstellationMsg;
 use selectors::states::*;
 use std::borrow::ToOwned;
 use std::cell::Cell;
@@ -64,7 +65,7 @@ pub struct HTMLInputElement {
     value_changed: Cell<bool>,
     size: Cell<u32>,
     #[ignore_heap_size_of = "#7193"]
-    textinput: DOMRefCell<TextInput<ConstellationChan>>,
+    textinput: DOMRefCell<TextInput<ConstellationChan<ConstellationMsg>>>,
     activation_state: DOMRefCell<InputActivationState>,
 }
 
diff --git a/components/script/dom/htmllinkelement.rs b/components/script/dom/htmllinkelement.rs
index a7365c38a69..bb470bf8d45 100644
--- a/components/script/dom/htmllinkelement.rs
+++ b/components/script/dom/htmllinkelement.rs
@@ -24,7 +24,7 @@ use encoding::all::UTF_8;
 use ipc_channel::ipc;
 use ipc_channel::router::ROUTER;
 use layout_interface::{LayoutChan, Msg};
-use msg::constellation_msg::Msg as ConstellationMsg;
+use msg::constellation_msg::ScriptMsg as ConstellationMsg;
 use msg::constellation_msg::{ConstellationChan, MozBrowserEvent};
 use net_traits::{AsyncResponseListener, AsyncResponseTarget, Metadata};
 use network_listener::{NetworkListener, PreInvoke};
diff --git a/components/script/dom/htmltextareaelement.rs b/components/script/dom/htmltextareaelement.rs
index 76194a2044e..f84b38ca55c 100644
--- a/components/script/dom/htmltextareaelement.rs
+++ b/components/script/dom/htmltextareaelement.rs
@@ -25,6 +25,7 @@ use dom::node::{document_from_node, window_from_node};
 use dom::nodelist::NodeList;
 use dom::virtualmethods::VirtualMethods;
 use msg::constellation_msg::ConstellationChan;
+use msg::constellation_msg::ScriptMsg as ConstellationMsg;
 use script_task::ScriptTaskEventCategory::InputEvent;
 use script_task::{CommonScriptMsg, Runnable};
 use selectors::states::*;
@@ -37,7 +38,7 @@ use util::str::DOMString;
 pub struct HTMLTextAreaElement {
     htmlelement: HTMLElement,
     #[ignore_heap_size_of = "#7193"]
-    textinput: DOMRefCell<TextInput<ConstellationChan>>,
+    textinput: DOMRefCell<TextInput<ConstellationChan<ConstellationMsg>>>,
     cols: Cell<u32>,
     rows: Cell<u32>,
     // https://html.spec.whatwg.org/multipage/#concept-textarea-dirty
diff --git a/components/script/dom/webglrenderingcontext.rs b/components/script/dom/webglrenderingcontext.rs
index a6da1d0d2ea..d21691f14af 100644
--- a/components/script/dom/webglrenderingcontext.rs
+++ b/components/script/dom/webglrenderingcontext.rs
@@ -31,7 +31,7 @@ use ipc_channel::ipc::{self, IpcSender};
 use js::jsapi::{JSContext, JSObject, RootedValue};
 use js::jsapi::{JS_GetFloat32ArrayData, JS_GetObjectAsArrayBufferView};
 use js::jsval::{BooleanValue, Int32Value, JSVal, NullValue, UndefinedValue};
-use msg::constellation_msg::Msg as ConstellationMsg;
+use msg::constellation_msg::ScriptMsg as ConstellationMsg;
 use net_traits::image::base::PixelFormat;
 use net_traits::image_cache_task::ImageResponse;
 use offscreen_gl_context::GLContextAttributes;
diff --git a/components/script/dom/window.rs b/components/script/dom/window.rs
index cf7c85a160f..4cf2bbe881f 100644
--- a/components/script/dom/window.rs
+++ b/components/script/dom/window.rs
@@ -43,6 +43,7 @@ use layout_interface::{ContentBoxResponse, ContentBoxesResponse, ResolvedStyleRe
 use layout_interface::{LayoutChan, LayoutRPC, Msg, Reflow, ReflowGoal, ReflowQueryType};
 use libc;
 use msg::compositor_msg::{LayerId, ScriptToCompositorMsg};
+use msg::constellation_msg::ScriptMsg as ConstellationMsg;
 use msg::constellation_msg::{ConstellationChan, LoadData, PipelineId, SubpageId, WindowSizeData, WorkerId};
 use msg::webdriver_msg::{WebDriverJSError, WebDriverJSResult};
 use net_traits::ResourceTask;
@@ -191,7 +192,7 @@ pub struct Window {
 
     /// A handle for communicating messages to the constellation task.
     #[ignore_heap_size_of = "channels are hard"]
-    constellation_chan: ConstellationChan,
+    constellation_chan: ConstellationChan<ConstellationMsg>,
 
     /// Pending scroll to fragment event, if any
     fragment_name: DOMRefCell<Option<String>>,
@@ -1071,7 +1072,7 @@ impl Window {
         self.layout_chan.clone()
     }
 
-    pub fn constellation_chan(&self) -> ConstellationChan {
+    pub fn constellation_chan(&self) -> ConstellationChan<ConstellationMsg> {
         self.constellation_chan.clone()
     }
 
@@ -1224,7 +1225,7 @@ impl Window {
                storage_task: StorageTask,
                mem_profiler_chan: mem::ProfilerChan,
                devtools_chan: Option<IpcSender<ScriptToDevtoolsControlMsg>>,
-               constellation_chan: ConstellationChan,
+               constellation_chan: ConstellationChan<ConstellationMsg>,
                scheduler_chan: IpcSender<TimerEventRequest>,
                timer_event_chan: IpcSender<TimerEvent>,
                layout_chan: LayoutChan,
diff --git a/components/script/dom/workerglobalscope.rs b/components/script/dom/workerglobalscope.rs
index 3e49836e970..96a1786ff3c 100644
--- a/components/script/dom/workerglobalscope.rs
+++ b/components/script/dom/workerglobalscope.rs
@@ -20,6 +20,7 @@ use dom::workernavigator::WorkerNavigator;
 use ipc_channel::ipc::IpcSender;
 use js::jsapi::{HandleValue, JSAutoRequest, JSContext};
 use js::rust::Runtime;
+use msg::constellation_msg::ScriptMsg as ConstellationMsg;
 use msg::constellation_msg::{ConstellationChan, PipelineId, WorkerId};
 use net_traits::{ResourceTask, load_whole_resource};
 use profile_traits::mem;
@@ -43,7 +44,7 @@ pub struct WorkerGlobalScopeInit {
     pub mem_profiler_chan: mem::ProfilerChan,
     pub to_devtools_sender: Option<IpcSender<ScriptToDevtoolsControlMsg>>,
     pub from_devtools_sender: Option<IpcSender<DevtoolScriptControlMsg>>,
-    pub constellation_chan: ConstellationChan,
+    pub constellation_chan: ConstellationChan<ConstellationMsg>,
     pub scheduler_chan: IpcSender<TimerEventRequest>,
     pub worker_id: WorkerId,
 }
@@ -84,7 +85,7 @@ pub struct WorkerGlobalScope {
     devtools_wants_updates: Cell<bool>,
 
     #[ignore_heap_size_of = "Defined in std"]
-    constellation_chan: ConstellationChan,
+    constellation_chan: ConstellationChan<ConstellationMsg>,
 
     #[ignore_heap_size_of = "Defined in std"]
     scheduler_chan: IpcSender<TimerEventRequest>,
@@ -135,7 +136,7 @@ impl WorkerGlobalScope {
         &self.from_devtools_receiver
     }
 
-    pub fn constellation_chan(&self) -> ConstellationChan {
+    pub fn constellation_chan(&self) -> ConstellationChan<ConstellationMsg> {
         self.constellation_chan.clone()
     }
 
diff --git a/components/script/layout_interface.rs b/components/script/layout_interface.rs
index 7c85d9c681e..cf9bae13e3b 100644
--- a/components/script/layout_interface.rs
+++ b/components/script/layout_interface.rs
@@ -14,6 +14,7 @@ use ipc_channel::ipc::{IpcReceiver, IpcSender};
 use libc::uintptr_t;
 use msg::compositor_msg::Epoch;
 use msg::compositor_msg::LayerId;
+use msg::constellation_msg::ScriptMsg as ConstellationMsg;
 use msg::constellation_msg::{ConstellationChan, Failure, PipelineId};
 use msg::constellation_msg::{WindowSizeData};
 use net_traits::image_cache_task::ImageCacheTask;
@@ -251,7 +252,7 @@ pub struct NewLayoutTaskInfo {
     pub is_parent: bool,
     pub layout_pair: OpaqueScriptLayoutChannel,
     pub pipeline_port: IpcReceiver<LayoutControlMsg>,
-    pub constellation_chan: ConstellationChan,
+    pub constellation_chan: ConstellationChan<ConstellationMsg>,
     pub failure: Failure,
     pub script_chan: Sender<ConstellationControlMsg>,
     pub image_cache_task: ImageCacheTask,
diff --git a/components/script/script_task.rs b/components/script/script_task.rs
index d2fc0a93917..5a12d9e004f 100644
--- a/components/script/script_task.rs
+++ b/components/script/script_task.rs
@@ -62,7 +62,7 @@ use layout_interface::{self, LayoutChan, NewLayoutTaskInfo, ReflowGoal, ScriptLa
 use libc;
 use mem::heap_size_of_self_and_children;
 use msg::compositor_msg::{EventResult, LayerId, ScriptToCompositorMsg};
-use msg::constellation_msg::Msg as ConstellationMsg;
+use msg::constellation_msg::ScriptMsg as ConstellationMsg;
 use msg::constellation_msg::{ConstellationChan, FocusType, LoadData};
 use msg::constellation_msg::{MozBrowserEvent, PipelineId};
 use msg::constellation_msg::{PipelineNamespace};
@@ -403,7 +403,7 @@ pub struct ScriptTask {
     control_port: Receiver<ConstellationControlMsg>,
 
     /// For communicating load url messages to the constellation
-    constellation_chan: ConstellationChan,
+    constellation_chan: ConstellationChan<ConstellationMsg>,
 
     /// A handle to the compositor for communicating ready state messages.
     compositor: DOMRefCell<IpcSender<ScriptToCompositorMsg>>,
diff --git a/components/script_traits/lib.rs b/components/script_traits/lib.rs
index 12ed3776bb5..337f07fda05 100644
--- a/components/script_traits/lib.rs
+++ b/components/script_traits/lib.rs
@@ -31,6 +31,7 @@ use euclid::rect::Rect;
 use ipc_channel::ipc::{IpcReceiver, IpcSender};
 use libc::c_void;
 use msg::compositor_msg::{Epoch, LayerId, ScriptToCompositorMsg};
+use msg::constellation_msg::ScriptMsg as ConstellationMsg;
 use msg::constellation_msg::{ConstellationChan, Failure, PipelineId, WindowSizeData};
 use msg::constellation_msg::{Key, KeyModifiers, KeyState, LoadData, SubpageId};
 use msg::constellation_msg::{MozBrowserEvent, PipelineNamespaceId};
@@ -253,7 +254,7 @@ pub struct InitialScriptState {
     /// A port on which messages sent by the constellation to script can be received.
     pub control_port: Receiver<ConstellationControlMsg>,
     /// A channel on which messages can be sent to the constellation from script.
-    pub constellation_chan: ConstellationChan,
+    pub constellation_chan: ConstellationChan<ConstellationMsg>,
     /// A channel to schedule timer events.
     pub scheduler_chan: IpcSender<TimerEventRequest>,
     /// Information that script sends out when it panics.
diff --git a/components/servo/lib.rs b/components/servo/lib.rs
index 359fc6a82ec..c43a22f2b21 100644
--- a/components/servo/lib.rs
+++ b/components/servo/lib.rs
@@ -48,12 +48,12 @@ extern crate libc;
 extern crate webdriver_server;
 
 #[cfg(feature = "webdriver")]
-fn webdriver(port: u16, constellation: msg::constellation_msg::ConstellationChan) {
+fn webdriver(port: u16, constellation: msg::constellation_msg::ConstellationChan<ConstellationMsg>) {
     webdriver_server::start_server(port, constellation.clone());
 }
 
 #[cfg(not(feature = "webdriver"))]
-fn webdriver(_port: u16, _constellation: msg::constellation_msg::ConstellationChan) { }
+fn webdriver(_port: u16, _constellation: msg::constellation_msg::ConstellationChan<ConstellationMsg>) { }
 
 use compositing::CompositorEventListener;
 use compositing::compositor_task::InitialCompositorState;
@@ -62,8 +62,8 @@ use compositing::windowing::WindowEvent;
 use compositing::windowing::WindowMethods;
 use compositing::{CompositorProxy, CompositorTask, Constellation};
 use gfx::font_cache_task::FontCacheTask;
+use msg::constellation_msg::CompositorMsg as ConstellationMsg;
 use msg::constellation_msg::ConstellationChan;
-use msg::constellation_msg::Msg as ConstellationMsg;
 use net::image_cache_task::new_image_cache_task;
 use net::resource_task::new_resource_task;
 use net::storage_task::StorageTaskFactory;
@@ -193,7 +193,7 @@ fn create_constellation(opts: opts::Opts,
                         time_profiler_chan: time::ProfilerChan,
                         mem_profiler_chan: mem::ProfilerChan,
                         devtools_chan: Option<Sender<devtools_traits::DevtoolsControlMsg>>,
-                        supports_clipboard: bool) -> ConstellationChan {
+                        supports_clipboard: bool) -> ConstellationChan<ConstellationMsg> {
     let resource_task = new_resource_task(opts.user_agent.clone(), devtools_chan.clone());
 
     let image_cache_task = new_image_cache_task(resource_task.clone());
diff --git a/components/webdriver_server/lib.rs b/components/webdriver_server/lib.rs
index 497e543b28d..71c6dea5f84 100644
--- a/components/webdriver_server/lib.rs
+++ b/components/webdriver_server/lib.rs
@@ -27,7 +27,7 @@ use hyper::method::Method::{self, Post};
 use image::{DynamicImage, ImageFormat, RgbImage};
 use ipc_channel::ipc::{self, IpcReceiver, IpcSender};
 use keys::keycodes_to_keys;
-use msg::constellation_msg::Msg as ConstellationMsg;
+use msg::constellation_msg::CompositorMsg as ConstellationMsg;
 use msg::constellation_msg::{ConstellationChan, FrameId, LoadData, PipelineId};
 use msg::constellation_msg::{NavigationDirection, PixelFormat, WebDriverCommandMsg};
 use msg::webdriver_msg::{LoadStatus, WebDriverFrameId, WebDriverJSError, WebDriverJSResult, WebDriverScriptCommand};
@@ -57,7 +57,7 @@ fn extension_routes() -> Vec<(Method, &'static str, ServoExtensionRoute)> {
                 (Post, "/session/{sessionId}/servo/prefs/reset", ServoExtensionRoute::ResetPrefs)]
 }
 
-pub fn start_server(port: u16, constellation_chan: ConstellationChan) {
+pub fn start_server(port: u16, constellation_chan: ConstellationChan<ConstellationMsg>) {
     let handler = Handler::new(constellation_chan);
     spawn_named("WebdriverHttpServer".to_owned(), move || {
         server::start(SocketAddr::new("0.0.0.0".parse().unwrap(), port), handler,
@@ -72,7 +72,7 @@ struct WebDriverSession {
 
 struct Handler {
     session: Option<WebDriverSession>,
-    constellation_chan: ConstellationChan,
+    constellation_chan: ConstellationChan<ConstellationMsg>,
     script_timeout: u32,
     load_timeout: u32,
     implicit_wait_timeout: u32
@@ -207,9 +207,8 @@ impl WebDriverSession {
     }
 }
 
-
 impl Handler {
-    pub fn new(constellation_chan: ConstellationChan) -> Handler {
+    pub fn new(constellation_chan: ConstellationChan<ConstellationMsg>) -> Handler {
         Handler {
             session: None,
             constellation_chan: constellation_chan,