Establish mojo service between Canvas (blink) and SurfaceManager (browser)

third_party/WebKit/Source/modules/canvas/HTMLCanvasElementModule.cpp

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "modules/canvas/HTMLCanvasElementModule.h"
 
 #include "core/dom/DOMNodeIds.h"
 #include "core/html/canvas/CanvasContextCreationAttributes.h"
 #include "core/html/canvas/CanvasRenderingContext.h"
 #include "core/offscreencanvas/OffscreenCanvas.h"
 
 namespace blink {
 
 void HTMLCanvasElementModule::getContext(HTMLCanvasElement& canvas, const String& type, const CanvasContextCreationAttributes& attributes, RenderingContext& result)
 {
     CanvasRenderingContext* context = canvas.getCanvasRenderingContext(type, attributes);
     if (context) {
         context->setCanvasGetContextResult(result);
     }
 }
 
 OffscreenCanvas* HTMLCanvasElementModule::transferControlToOffscreen(HTMLCanvasElement& canvas, ExceptionState& exceptionState)
 {
+    OffscreenCanvas* offscreenCanvas = transferControlToOffscreenInternal(canvas, exceptionState);
+
+    if (!canvas.createSurfaceLayer()) {
+        exceptionState.throwDOMException(V8GeneralError, "Layer creation for offscreen canvas fails.");

[Justin Novosad, 2016/06/10 18:48:15]

Nit: fails->failed
Also I don't think we should mention layers here: the user has no concept of
layers around this API. This is caused by an IPC timeout, right? Perhaps we want
to give users a bit of an explanation so that they know it's not their code that
has an error. Perhaps: "Offscreen canvas creation failed due to an internal
timeout."

+    }
+
+    return offscreenCanvas;
+}
+
+OffscreenCanvas* HTMLCanvasElementModule::transferControlToOffscreenInternal(HTMLCanvasElement& canvas, ExceptionState& exceptionState)
+{
     if (canvas.renderingContext()) {
         exceptionState.throwDOMException(InvalidStateError, "Cannot transfer control from a canvas that has a rendering context.");
         return nullptr;
     }
     OffscreenCanvas* offscreenCanvas = OffscreenCanvas::create(canvas.width(), canvas.height());
     offscreenCanvas->setAssociatedCanvasId(DOMNodeIds::idForNode(&canvas));
-    canvas.createSurfaceLayerBridge();
     return offscreenCanvas;
 }
 
 }