The issue is observed is on ChromeOS and not Windows.

As per comment #1, as this issue is seen on Chrome OS and not on Windows, marking Chrome OS for further triaging.

Thanks..

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/57d32bfc804544458a698295d97529a058009990

commit 57d32bfc804544458a698295d97529a058009990
Author: Shirish S <shirish.s@amd.com>
Date: Sat Jan 06 00:53:27 2018

Fix WebGL performance regression on AMD Stoney platform

The regression is caused since the below commit:
"cdc786f5d2a2 Use 8x MSAA rather than 4x MSAA when available."

It has been found that althogh 8x improves the image quality
but leads to a performance regression of around 30%.
Hence to resolve the same this patch introduces a workaround
to limit the MSAA max sample count to 4x, for AMD platform _only_.

Added self to AUTHORS

BUG= chromium:798936 ,b:70820067
TEST=test_that graphics_WebGLAquarium
     results :
     avg_fps_0050_fishes=59.2230100192
     avg_fps_1000_fishes=56.5302789847

Change-Id: I3133c558ee641f126e2f932a8398d4ae4855f392
Signed-off-by: Shirish S <shirish.s@amd.com>
Reviewed-on: https://chromium-review.googlesource.com/846639
Commit-Queue: Kenneth Russell <kbr@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#527464}
[modify] https://crrev.com/57d32bfc804544458a698295d97529a058009990/AUTHORS
[modify] https://crrev.com/57d32bfc804544458a698295d97529a058009990/gpu/config/gpu_driver_bug_list.json
[modify] https://crrev.com/57d32bfc804544458a698295d97529a058009990/gpu/config/gpu_driver_bug_workaround_type.h
[modify] https://crrev.com/57d32bfc804544458a698295d97529a058009990/third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.cpp

Issue has not been modified or commented on in the last 365 days, please re-open or file a new bug if this is still an issue.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot