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

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

Index: third_party/WebKit/Source/modules/canvas/HTMLCanvasElementModule.cpp
diff --git a/third_party/WebKit/Source/modules/canvas/HTMLCanvasElementModule.cpp b/third_party/WebKit/Source/modules/canvas/HTMLCanvasElementModule.cpp
index f22f6ef226bdf3da08e997975c64cb196fc3bf6c..f4fbf82971484a94532f49e63830f76c7783bf1c 100644
--- a/third_party/WebKit/Source/modules/canvas/HTMLCanvasElementModule.cpp
+++ b/third_party/WebKit/Source/modules/canvas/HTMLCanvasElementModule.cpp
@@ -21,13 +21,23 @@ void HTMLCanvasElementModule::getContext(HTMLCanvasElement& canvas, const String
 
 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;
 }