The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/903a3a827ddbf8dc46ada202c6768a997860c7bf

commit 903a3a827ddbf8dc46ada202c6768a997860c7bf
Author: xlai <xlai@chromium.org>
Date: Thu Aug 11 23:39:29 2016

Updates on canvas backreference on canvas rendering contexts

Based on recent proposal (https://wiki.whatwg.org/wiki/OffscreenCanvas) change,
the backreference to either html canvas or offscreen canvas should be named as
"canvas" consistently for all rendering contexts.

This CL changes the the different name "offscreencanvas" in
OffscreenCanvasRenderingContext2D. Also, this CL allows Webgl rendering contexts
that are created from OffscreenCanvas to return the OffscreenCanvas, and those
that are created from HTMLCanvas to return the HTMLCanvasElement, via the same
"canvas" attribute.

BUG= 637022 
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.win:win_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel

Review-Url: https://codereview.chromium.org/2221173003
Cr-Commit-Position: refs/heads/master@{#411444}

[add] https://crrev.com/903a3a827ddbf8dc46ada202c6768a997860c7bf/third_party/WebKit/LayoutTests/fast/canvas/rendering-contexts-back-references.html
[modify] https://crrev.com/903a3a827ddbf8dc46ada202c6768a997860c7bf/third_party/WebKit/LayoutTests/http/tests/serviceworker/webexposed/global-interface-listing-service-worker-expected.txt
[modify] https://crrev.com/903a3a827ddbf8dc46ada202c6768a997860c7bf/third_party/WebKit/LayoutTests/webexposed/global-interface-listing-dedicated-worker-expected.txt
[modify] https://crrev.com/903a3a827ddbf8dc46ada202c6768a997860c7bf/third_party/WebKit/LayoutTests/webexposed/global-interface-listing-expected.txt
[modify] https://crrev.com/903a3a827ddbf8dc46ada202c6768a997860c7bf/third_party/WebKit/LayoutTests/webexposed/global-interface-listing-shared-worker-expected.txt
[modify] https://crrev.com/903a3a827ddbf8dc46ada202c6768a997860c7bf/third_party/WebKit/Source/bindings/modules/v8/generated.gni
[modify] https://crrev.com/903a3a827ddbf8dc46ada202c6768a997860c7bf/third_party/WebKit/Source/modules/offscreencanvas2d/OffscreenCanvasRenderingContext2D.idl
[modify] https://crrev.com/903a3a827ddbf8dc46ada202c6768a997860c7bf/third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp
[modify] https://crrev.com/903a3a827ddbf8dc46ada202c6768a997860c7bf/third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.h
[modify] https://crrev.com/903a3a827ddbf8dc46ada202c6768a997860c7bf/third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.idl