The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/ecf58aa7eb349ab2b4beaec613183810c4edf135

commit ecf58aa7eb349ab2b4beaec613183810c4edf135
Author: xidachen <xidachen@chromium.org>
Date: Fri Mar 04 16:56:29 2016

Add "premultiply" in ImageBitmapOptions enum PremultiplyAlpha

At this moment, there are two options of "none" and "default", this CL
adds "premultiply". The code path for "premultiply" and "default" is the
same so we can avoid large changes of any existing C++ code. Layout tests has
been created to reflect this additional option.

Locally I have added this option to all the conformance tests for
ImageBitmap hosted by KhronosGroup/WebGL, and they all pass.
Once this CL landed, there will be a pull request to update those tests.

BUG= 591713 

Review URL: https://codereview.chromium.org/1756963003

Cr-Commit-Position: refs/heads/master@{#379302}

[modify] https://crrev.com/ecf58aa7eb349ab2b4beaec613183810c4edf135/third_party/WebKit/LayoutTests/fast/canvas/canvas-createImageBitmap-drawImage-video-with-options-expected.txt
[modify] https://crrev.com/ecf58aa7eb349ab2b4beaec613183810c4edf135/third_party/WebKit/LayoutTests/fast/canvas/canvas-createImageBitmap-drawImage-video-with-options.html
[modify] https://crrev.com/ecf58aa7eb349ab2b4beaec613183810c4edf135/third_party/WebKit/LayoutTests/fast/canvas/canvas-createImageBitmap-drawImage-with-options-expected.txt
[modify] https://crrev.com/ecf58aa7eb349ab2b4beaec613183810c4edf135/third_party/WebKit/LayoutTests/fast/canvas/canvas-createImageBitmap-drawImage-with-options.html
[modify] https://crrev.com/ecf58aa7eb349ab2b4beaec613183810c4edf135/third_party/WebKit/Source/core/frame/ImageBitmap.cpp
[modify] https://crrev.com/ecf58aa7eb349ab2b4beaec613183810c4edf135/third_party/WebKit/Source/core/imagebitmap/ImageBitmapOptions.idl