xlai: can you take a look at this?  It only fails on one phone, so we might be triggering a driver issue (or could be us not handling something correctly).

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/47f1fb204582c356c19ab85a296e0dab790fb80c

commit 47f1fb204582c356c19ab85a296e0dab790fb80c
Author: zmo <zmo@chromium.org>
Date: Thu Feb 16 18:56:37 2017

Mark a newly added test as fail on Nexus 6

conformance/offscreencanvas/context-attribute-preserve-drawing-buffer.html

BUG= 693135 
TEST=bot
NOTRY=true
TBR=xlai@chromium.org
CQ_INCLUDE_TRYBOTS=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;master.tryserver.chromium.android:android_optional_gpu_tests_rel

Review-Url: https://codereview.chromium.org/2702573002
Cr-Commit-Position: refs/heads/master@{#451032}

[modify] https://crrev.com/47f1fb204582c356c19ab85a296e0dab790fb80c/content/test/gpu/gpu_tests/webgl_conformance_expectations.py

 Issue 693201  has been merged into this issue.

Currently fserb@ commented out this suppression in webgl_conformance_expectations.py due to commit() implementation change.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/539ef7dd7cb70fc0fa684c44c0bfce18ced47e61

commit 539ef7dd7cb70fc0fa684c44c0bfce18ced47e61
Author: Corentin Wallez <cwallez@chromium.org>
Date: Tue Nov 13 17:08:12 2018

Add back some WebGL test expectations

A lot of expectations were removed but some of them were still
necessary, this adds them back.

TBR=kbr@chromium.org
BUG= chromium:693135 
BUG=chromium:772651
BUG= chromium:798117 
BUG= chromium:874620 
BUG=chromium:887241

Change-Id: Ib3bccdf2ff48a28a8f0a3ce428239980a58c5266
Reviewed-on: https://chromium-review.googlesource.com/c/1333650
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#607626}
[modify] https://crrev.com/539ef7dd7cb70fc0fa684c44c0bfce18ced47e61/content/test/gpu/gpu_tests/webgl2_conformance_expectations.py
[modify] https://crrev.com/539ef7dd7cb70fc0fa684c44c0bfce18ced47e61/content/test/gpu/gpu_tests/webgl_conformance_expectations.py