Add rendering context and rendering 2D context to OffscreenCanvas

third_party/WebKit/Source/modules/offscreencanvas2d/OffscreenCanvasRenderingContext2D.idl

Index: third_party/WebKit/Source/modules/offscreencanvas2d/OffscreenCanvasRenderingContext2D.idl
diff --git a/third_party/WebKit/Source/modules/imagebitmap/ImageBitmapRenderingContext.idl b/third_party/WebKit/Source/modules/offscreencanvas2d/OffscreenCanvasRenderingContext2D.idl
similarity index 46%
copy from third_party/WebKit/Source/modules/imagebitmap/ImageBitmapRenderingContext.idl
copy to third_party/WebKit/Source/modules/offscreencanvas2d/OffscreenCanvasRenderingContext2D.idl
index ac6f794a3cbc2519847870de0ee1f43e30a3e946..5c33a575d9ff207ad3753de515edbbc2430d3c0e 100644
--- a/third_party/WebKit/Source/modules/imagebitmap/ImageBitmapRenderingContext.idl
+++ b/third_party/WebKit/Source/modules/offscreencanvas2d/OffscreenCanvasRenderingContext2D.idl
@@ -2,13 +2,15 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// Note: The official spec is WIP at wiki.whatwg.org/wiki/OffscreenCanvas.
+
 [
+    GarbageCollected,
+    Exposed=(Window,Worker),
     RuntimeEnabled=ExperimentalCanvasFeatures,
-    SetWrapperReferenceFrom=canvas,
-    WillBeGarbageCollected,
-] interface ImageBitmapRenderingContext {
+] interface OffscreenCanvasRenderingContext2D {
     // back-reference to the canvas
-    readonly attribute HTMLCanvasElement canvas;
-
-    void transferImageBitmap(ImageBitmap bitmap);
+    readonly attribute OffscreenCanvas offscreenCanvas;
 };
+
+OffscreenCanvasRenderingContext2D implements CanvasPathMethods;