The only blink change in the regression range is for canvas color management. Could we please re-do the bisect, it doesn't look right.

Able to reproduce this issue on windows 7, Mac 10.12.2,Linux Ubuntu 14.04 with Chrome stable version-55.0.2883.87 and Canary-57.0.2969.0. Please find the below per revision Bisect information:

Manual Bisect:
-------------
Bad-54.0.2839.0 --Revision--414243
Good-54.0.2838.0-- Revision--413929

Bisect Tool Info:
-----------------
You are probably looking for a change made after 414107 (known good), but no later than 414108 (first known bad).

CHANGELOG URL:
------------------
The script might not always return single CL as suspectas some perf builds might get missing due to failure.

 https://chromium.googlesource.com/chromium/src/+log/7a5d260eaadd7efcc073564b94c5c91e1856110d..d5e03be7f3be92a1940c19aab0664ca02ce1011f

Possible suspect:
------------------
https://chromium.googlesource.com/chromium/src/+/d5e03be7f3be92a1940c19aab0664ca02ce1011f

Review-Url: 
-----------
https://codereview.chromium.org/2212163002

junov@ Kindly take a look and please help us to reassign this issue to a right owner if not with respect to this change.

Thanks.!

Thanks for verifying. Given that two different bisect runs point to r414108 as the culprit assigning this to junov seems like the right thing to do.

Here is a reduced test case: https://jsfiddle.net/y7jmapj2/

The bug is basically that setting a CSS box shadow on a canvas with a webgl context created with {alpha:false} will cause the box shadow to render as opaque black.

I have no idea how r414108 regressed this, but that CL does touch the plumbing of the "alpha" context creation attribute...

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/7cfe269af863d9726b70c316ffbcc1f9f41dfe69

commit 7cfe269af863d9726b70c316ffbcc1f9f41dfe69
Author: junov <junov@chromium.org>
Date: Fri Jan 13 17:53:06 2017

Fix box shadow rendering on opaque WebGL canvases

BUG= 677372 
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2

Review-Url: https://codereview.chromium.org/2629083003
Cr-Commit-Position: refs/heads/master@{#443604}

[modify] https://crrev.com/7cfe269af863d9726b70c316ffbcc1f9f41dfe69/third_party/WebKit/LayoutTests/compositing/draws-content/canvas-background-layer-expected.txt
[modify] https://crrev.com/7cfe269af863d9726b70c316ffbcc1f9f41dfe69/third_party/WebKit/LayoutTests/compositing/draws-content/canvas-background-layer.html
[add] https://crrev.com/7cfe269af863d9726b70c316ffbcc1f9f41dfe69/third_party/WebKit/LayoutTests/fast/canvas/webgl/webgl-shadow-no-alpha-expected.html
[add] https://crrev.com/7cfe269af863d9726b70c316ffbcc1f9f41dfe69/third_party/WebKit/LayoutTests/fast/canvas/webgl/webgl-shadow-no-alpha.html
[modify] https://crrev.com/7cfe269af863d9726b70c316ffbcc1f9f41dfe69/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp

Verified on Mac OS 10.12.2 ,Ubuntu 14.04 and windows 7 using chrome dev M57 #57.0.2984.0 and issue is fixed.
Observed that the Footer text not overlapped with video box.

Attached screen-cast for reference.

Adding TE-Verified Labels.

Thanks!

Deleted: 677372.ogv 3.7 MB

	677372.ogv 3.7 MB View Download