Implement OffscreenCanvas.getContext('webgl')

third_party/WebKit/Source/modules/offscreencanvas/OffscreenCanvas.idl

 // Copyright 2015 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.
 
 // Note: If there're more context types implemented, they should be added here
 // to form a union type of OffscreenCanvasRenderingContext
-typedef OffscreenCanvasRenderingContext2D OffscreenRenderingContext;
-
+typedef (OffscreenCanvasRenderingContext2D or
+         WebGLRenderingContext or
+         WebGL2RenderingContext) OffscreenRenderingContext;

[Justin Novosad, 2016/04/20 20:07:27]

WebGL2RenderingContext creation is not covered by layout tests.

[xidachen, 2016/04/20 20:52:09]

I think we should start with small CLs, so this CL implements
getContext('webgl') only, and getContext('webgl2') is not implemented. Since
webgl2 is still experimental, I think we can leave it until webgl API works.

 [
     Constructor([EnforceRange] unsigned long width, [EnforceRange] unsigned long height),
     Exposed=(Window,Worker),
     RuntimeEnabled=ExperimentalCanvasFeatures,
 ] interface OffscreenCanvas {
     [EnforceRange] attribute unsigned long width;
     [EnforceRange] attribute unsigned long height;
 
-    OffscreenRenderingContext? getContext(DOMString contextId, optional CanvasContextCreationAttributes attributes);
+    [CallWith=ScriptState] OffscreenRenderingContext? getContext(DOMString contextId, optional CanvasContextCreationAttributes attributes);

[xlai (Olivia), 2016/04/20 20:42:16]

I can see that the only reason that you added [CallWith=ScriptState] here (and
one more new parameter to many corresponding functions in Factory, 2D, Webgl
etc) is to eventually use the ExecutionState in
WebGLRenderingContextBase::createWebGraphicsContext3DProviderHelper. But I think
you can obtain ScriptState* by just using
ScriptState::current(v8::Isolate::GetCurrent()). (Example:
WebDocument::registerEmbedderCustomElement()).
Otherwise, you can also change to CallWith=ExecutionContext.

[xidachen, 2016/04/20 20:52:09]

Thank you for the suggestion, will do that.

     [RaisesException] ImageBitmap transferToImageBitmap();
 };