Auto merge of #17891 - MortimerGoro:webgl_move, r=glennw,emilio

Improved WebGL architecture

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Info about the big picture and the goals of the WebGL refactor in this thread: https://groups.google.com/forum/#!topic/mozilla.dev.servo/0WMGz60kKzQ

I tried to reduce this PR as much as possible as requested in the thread. I'll do separate PRs for other features (e.g.: Batch messages or use shared memory to improve frame times) or fixes.

Some tips to ease the review process:
- Most changes in DOM objects follow the same pattern (remove CanvasMsg wrapper and use the new sender method).
- WebGLCommands are the same ones as before (moved from webrender_api). So those lines are already reviewed.
- See WebGL traits in [components/canvas_traits/webgl.rs](https://github.com/servo/servo/pull/17891/files#diff-8701045d01505418701d0631d4d45562)
- See WebGLThread and WR External Image bridge in [components/canvas/webgl_thread.rs](https://github.com/servo/servo/pull/17891/files#diff-281554879f39a2a041f7a69d442a5d2e)
- The implementation submitted in this PR creates a single `WebGLThread` for all ScriptThread/Pipelines. See that in [components/canvas/webgl_mode/inprocess.rs](https://github.com/servo/servo/pull/17891/files#diff-250070c6c5a38c7f9fa0f5b3c101f68b)

The conformance tests will help to guarantee that we don't miss anything.

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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [ ] These changes fix #__ (github issue number if applicable).

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- [x] There are tests for these changes OR
- [ ] These changes do not require tests because _____

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1 files changed, 16 insertions, 20 deletions

diff --git a/components/script/dom/vrdisplay.rs b/components/script/dom/vrdisplay.rs
index 54f06fb928f..a36bd27ad29 100644
--- a/components/script/dom/vrdisplay.rs
+++ b/components/script/dom/vrdisplay.rs
@@ -2,7 +2,7 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-use canvas_traits::CanvasMsg;
+use canvas_traits::webgl::{webgl_channel, WebGLReceiver, WebVRCommand};
 use core::ops::Deref;
 use dom::bindings::callback::ExceptionHandling;
 use dom::bindings::cell::DOMRefCell;
@@ -32,8 +32,7 @@ use dom::vrpose::VRPose;
 use dom::vrstageparameters::VRStageParameters;
 use dom::webglrenderingcontext::WebGLRenderingContext;
 use dom_struct::dom_struct;
-use ipc_channel::ipc;
-use ipc_channel::ipc::{IpcSender, IpcReceiver};
+use ipc_channel::ipc::{self, IpcSender};
 use js::jsapi::JSContext;
 use script_runtime::CommonScriptMsg;
 use script_runtime::ScriptThreadEventCategory::WebVREvent;
@@ -43,7 +42,6 @@ use std::mem;
 use std::rc::Rc;
 use std::sync::mpsc;
 use std::thread;
-use webrender_api::VRCompositorCommand;
 use webvr_traits::{WebVRDisplayData, WebVRDisplayEvent, WebVRFrameData, WebVRLayer, WebVRMsg};
 
 #[dom_struct]
@@ -71,7 +69,7 @@ pub struct VRDisplay {
     // Compositor VRFrameData synchonization
     frame_data_status: Cell<VRFrameDataStatus>,
     #[ignore_heap_size_of = "channels are hard"]
-    frame_data_receiver: DOMRefCell<Option<IpcReceiver<Result<Vec<u8>, ()>>>>,
+    frame_data_receiver: DOMRefCell<Option<WebGLReceiver<Result<Vec<u8>, ()>>>>,
     running_display_raf: Cell<bool>,
     paused: Cell<bool>,
     stopped_on_pause: Cell<bool>,
@@ -386,11 +384,10 @@ impl VRDisplayMethods for VRDisplay {
             return;
         }
 
-        let api_sender = self.layer_ctx.get().unwrap().ipc_renderer();
-        let display_id = self.display.borrow().display_id as u64;
+        let display_id = self.display.borrow().display_id;
         let layer = self.layer.borrow();
-        let msg = VRCompositorCommand::SubmitFrame(display_id, layer.left_bounds, layer.right_bounds);
-        api_sender.send(CanvasMsg::WebVR(msg)).unwrap();
+        let msg = WebVRCommand::SubmitFrame(display_id, layer.left_bounds, layer.right_bounds);
+        self.layer_ctx.get().unwrap().send_vr_command(msg);
     }
 
     // https://w3c.github.io/webvr/spec/1.1/#dom-vrdisplay-getlayers
@@ -489,11 +486,11 @@ impl VRDisplay {
 
     fn init_present(&self) {
         self.presenting.set(true);
-        let (sync_sender, sync_receiver) = ipc::channel().unwrap();
+        let (sync_sender, sync_receiver) = webgl_channel().unwrap();
         *self.frame_data_receiver.borrow_mut() = Some(sync_receiver);
 
-        let display_id = self.display.borrow().display_id as u64;
-        let api_sender = self.layer_ctx.get().unwrap().ipc_renderer();
+        let display_id = self.display.borrow().display_id;
+        let api_sender = self.layer_ctx.get().unwrap().webgl_sender();
         let js_sender = self.global().script_chan();
         let address = Trusted::new(&*self);
         let near_init = self.depth_near.get();
@@ -511,7 +508,7 @@ impl VRDisplay {
             let mut far = far_init;
 
             // Initialize compositor
-            api_sender.send(CanvasMsg::WebVR(VRCompositorCommand::Create(display_id))).unwrap();
+            api_sender.send_vr(WebVRCommand::Create(display_id)).unwrap();
             loop {
                 // Run RAF callbacks on JavaScript thread
                 let msg = box NotifyDisplayRAF {
@@ -521,8 +518,8 @@ impl VRDisplay {
                 js_sender.send(CommonScriptMsg::RunnableMsg(WebVREvent, msg)).unwrap();
 
                 // Run Sync Poses in parallell on Render thread
-                let msg = VRCompositorCommand::SyncPoses(display_id, near, far, sync_sender.clone());
-                api_sender.send(CanvasMsg::WebVR(msg)).unwrap();
+                let msg = WebVRCommand::SyncPoses(display_id, near, far, sync_sender.clone());
+                api_sender.send_vr(msg).unwrap();
 
                 // Wait until both SyncPoses & RAF ends
                 if let Ok(depth) = raf_receiver.recv().unwrap() {
@@ -541,10 +538,9 @@ impl VRDisplay {
         self.presenting.set(false);
         *self.frame_data_receiver.borrow_mut() = None;
 
-        let api_sender = self.layer_ctx.get().unwrap().ipc_renderer();
-        let display_id = self.display.borrow().display_id as u64;
-        let msg = VRCompositorCommand::Release(display_id);
-        api_sender.send(CanvasMsg::WebVR(msg)).unwrap();
+        let api_sender = self.layer_ctx.get().unwrap().webgl_sender();
+        let display_id = self.display.borrow().display_id;
+        api_sender.send_vr(WebVRCommand::Release(display_id)).unwrap();
     }
 
     // Only called when the JSContext is destroyed while presenting.
@@ -627,7 +623,7 @@ impl Runnable for NotifyDisplayRAF {
 }
 
 
-// WebVR Spect: If the number of values in the leftBounds/rightBounds arrays
+// WebVR Spec: If the number of values in the leftBounds/rightBounds arrays
 // is not 0 or 4 for any of the passed layers the promise is rejected
 fn parse_bounds(src: &Option<Vec<Finite<f32>>>, dst: &mut [f32; 4]) -> Result<(), &'static str> {
     match *src {