The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/a2095f6c1946afe6c434cf05eb4d419dd9b74275

commit a2095f6c1946afe6c434cf05eb4d419dd9b74275
Author: xlai <xlai@chromium.org>
Date: Mon Mar 27 18:12:46 2017

Synchronize commits at end of JS task

This CL defers the submission of frames to the end of a JS task, so that the
commits() for multiple OffscreenCanvases in the same execution context are
happening at the same time.

When a commit() comes in, there are three possible scenarios:
1. This is first commit since last resolved promise. In this case, we store the
   frame at m_currentFrame and register the context to task observer.
2. This is not the first commit for the same canvas in the same JS task. In
   this case, we overwrite the m_currentFrame but we do not duplicate
   registration to task observer.
3. This is the overdraw commit (the m_currentFrame has been dispatched but we
   are still waiting for the next OnBeginFrame to resolve the promise). In this
   case, we set the m_overdraw commit.

When JS task finishes, finalizeFrame() will get fired and submit the
current frame.

When OnBeginFrame is fired, we'll resolve the promise if there is no current
frame and no overdraw frame. If there is an overdraw frame, we doCommit for
the overdraw frame and wait for next animation frame to resolve the promise.

I've also modified the GPU pixel tests to test for all these situations.

BUG= 697582 
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.android:android_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel

Review-Url: https://codereview.chromium.org/2778483002
Cr-Commit-Position: refs/heads/master@{#459828}

[modify] https://crrev.com/a2095f6c1946afe6c434cf05eb4d419dd9b74275/content/test/data/gpu/pixel_offscreenCanvas_2d_commit_main.html
[modify] https://crrev.com/a2095f6c1946afe6c434cf05eb4d419dd9b74275/content/test/data/gpu/pixel_offscreenCanvas_2d_commit_worker.html
[modify] https://crrev.com/a2095f6c1946afe6c434cf05eb4d419dd9b74275/content/test/data/gpu/pixel_offscreenCanvas_webgl_commit_main.html
[modify] https://crrev.com/a2095f6c1946afe6c434cf05eb4d419dd9b74275/content/test/data/gpu/pixel_offscreenCanvas_webgl_commit_worker.html
[modify] https://crrev.com/a2095f6c1946afe6c434cf05eb4d419dd9b74275/content/test/gpu/gpu_tests/pixel_expectations.py
[modify] https://crrev.com/a2095f6c1946afe6c434cf05eb4d419dd9b74275/content/test/gpu/gpu_tests/pixel_test_pages.py
[modify] https://crrev.com/a2095f6c1946afe6c434cf05eb4d419dd9b74275/third_party/WebKit/LayoutTests/fast/canvas/OffscreenCanvas-placeholder-image-source-with-worker.html
[modify] https://crrev.com/a2095f6c1946afe6c434cf05eb4d419dd9b74275/third_party/WebKit/Source/core/html/canvas/CanvasRenderingContext.cpp
[modify] https://crrev.com/a2095f6c1946afe6c434cf05eb4d419dd9b74275/third_party/WebKit/Source/core/html/canvas/CanvasRenderingContext.h
[modify] https://crrev.com/a2095f6c1946afe6c434cf05eb4d419dd9b74275/third_party/WebKit/Source/core/offscreencanvas/OffscreenCanvas.cpp
[modify] https://crrev.com/a2095f6c1946afe6c434cf05eb4d419dd9b74275/third_party/WebKit/Source/core/offscreencanvas/OffscreenCanvas.h

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/772204b647bb8089ed2017718cc4afdeac1d80d1

commit 772204b647bb8089ed2017718cc4afdeac1d80d1
Author: xlai <xlai@chromium.org>
Date: Tue Mar 28 23:34:15 2017

Shrink the reference image dimension in OffscreenCanvas tests

The android device has a screen resolution width of 1080 and
devicePixelRatio of 2.625. As a result, the width of 600 in the
existing gpu pixel tests is too big as width * devicePixelRatio
> screen resolution. Therefore, I shrink the test rect to 400 in
width.

BUG= 697582 
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.android:android_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel

Review-Url: https://codereview.chromium.org/2774423006
Cr-Commit-Position: refs/heads/master@{#460237}

[modify] https://crrev.com/772204b647bb8089ed2017718cc4afdeac1d80d1/content/test/data/gpu/pixel_offscreenCanvas_2d_commit_main.html
[modify] https://crrev.com/772204b647bb8089ed2017718cc4afdeac1d80d1/content/test/data/gpu/pixel_offscreenCanvas_2d_commit_worker.html
[modify] https://crrev.com/772204b647bb8089ed2017718cc4afdeac1d80d1/content/test/data/gpu/pixel_offscreenCanvas_webgl_commit_main.html
[modify] https://crrev.com/772204b647bb8089ed2017718cc4afdeac1d80d1/content/test/data/gpu/pixel_offscreenCanvas_webgl_commit_worker.html
[modify] https://crrev.com/772204b647bb8089ed2017718cc4afdeac1d80d1/content/test/gpu/gpu_tests/pixel_test_pages.py

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/f2cdf4645352446d423e8b7c286870bcb7d00797

commit f2cdf4645352446d423e8b7c286870bcb7d00797
Author: xlai <xlai@chromium.org>
Date: Wed Mar 29 16:52:48 2017

Remove failed entries in gpu pixel expectations

TBR=zmo@chromium.org
TBR_REASON=Updating test expectations after reference images are generated
BUG= 697582 
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.android:android_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel

Review-Url: https://codereview.chromium.org/2777763005
Cr-Commit-Position: refs/heads/master@{#460425}

[modify] https://crrev.com/f2cdf4645352446d423e8b7c286870bcb7d00797/content/test/gpu/gpu_tests/pixel_expectations.py

There are still test rect dimension issue of these gpu pixel tests on Nexus 5 but the solution is simply to shrink the size. Moved to https://bugs.chromium.org/p/chromium/issues/detail?id=706647 as a separate issue then.