Eliminate ScrollRootId

Just use WebRender's ClipId directly. This will allow us to create and
use ReferenceFrames in the future, if we need to do that. It will also
make it easier to have Servo responsible for creating the root
scrolling area, which will allow removing some old hacks in the future.

1 files changed, 9 insertions, 7 deletions

diff --git a/components/layout_thread/lib.rs b/components/layout_thread/lib.rs
index 286d49484f6..fe6e6d0dea2 100644
--- a/components/layout_thread/lib.rs
+++ b/components/layout_thread/lib.rs
@@ -49,7 +49,7 @@ use gfx::display_list::{OpaqueNode, WebRenderImageInfo};
 use gfx::font;
 use gfx::font_cache_thread::FontCacheThread;
 use gfx::font_context;
-use gfx_traits::{Epoch, FragmentType, ScrollRootId};
+use gfx_traits::{Epoch, node_id_from_clip_id};
 use heapsize::HeapSizeOf;
 use ipc_channel::ipc::{self, IpcReceiver, IpcSender};
 use ipc_channel::router::ROUTER;
@@ -514,6 +514,7 @@ impl LayoutThread {
             ThreadLocalStyleContextCreationInfo::new(self.new_animations_sender.clone());
 
         LayoutContext {
+            id: self.id,
             style_context: SharedStyleContext {
                 stylist: rw_data.stylist.clone(),
                 options: StyleSystemOptions::default(),
@@ -1282,7 +1283,8 @@ impl LayoutThread {
             },
             ReflowQueryType::NodeScrollRootIdQuery(node) => {
                 let node = unsafe { ServoLayoutNode::new(&node) };
-                rw_data.scroll_root_id_response = Some(process_node_scroll_root_id_request(node));
+                rw_data.scroll_root_id_response = Some(process_node_scroll_root_id_request(self.id,
+                                                                                           node));
             },
             ReflowQueryType::ResolvedStyleQuery(node, ref pseudo, ref property) => {
                 let node = unsafe { ServoLayoutNode::new(&node) };
@@ -1339,12 +1341,12 @@ impl LayoutThread {
             let offset = new_scroll_state.scroll_offset;
             layout_scroll_states.insert(new_scroll_state.scroll_root_id, offset);
 
-            if new_scroll_state.scroll_root_id == ScrollRootId::root() {
+            if new_scroll_state.scroll_root_id.is_root_scroll_node() {
                 script_scroll_states.push((UntrustedNodeAddress::from_id(0), offset))
-            } else if !new_scroll_state.scroll_root_id.is_special() &&
-                    new_scroll_state.scroll_root_id.fragment_type() == FragmentType::FragmentBody {
-                let id = new_scroll_state.scroll_root_id.id();
-                script_scroll_states.push((UntrustedNodeAddress::from_id(id), offset))
+            } else if let Some(id) = new_scroll_state.scroll_root_id.external_id() {
+                if let Some(node_id) = node_id_from_clip_id(id as usize) {
+                    script_scroll_states.push((UntrustedNodeAddress::from_id(node_id), offset))
+                }
             }
         }
         let _ = self.script_chan