All graphs for this bug:
  https://chromeperf.appspot.com/group_report?bug_id=756572

(For debugging:) Original alerts at time of bug-filing:
  https://chromeperf.appspot.com/group_report?sid=4f13b6219a433f4757285bc3ee964738c61326384fd601cb833c74bbf95d0169


Bot(s) for this bug's original alert(s):

android-webview-nexus6

Started bisect job https://chromeperf.appspot.com/buildbucket_job_status/8970984279264140080

This regression is unrelated to the one in 755229. It was bisected to https://chromium.googlesource.com/chromium/src/+/037613aa74af94a82dce77e1e246f1f5364c0cfa.

Interesting. This change should not have perf side effects. Thanks for reporting. I'll look into that.

IIUC, this change enabled color correct conversions for canvas2D right?

Looking at the trace, I see that main frames are taking slightly longer now. From ~110ms to ~126ms, which I suspect is the additional cost from color conversions. If the result was cached, then you shouldn't have seen an impact. But if we were re-decoding every frame, then this change adds that additional cost from the color conversion step to every frame as well.

Actually, color correct rendering converts everything to SRGB, only if they are in any other color space. The reported test does not use a non-SRGB resource, so it should not take effect from this change. I'll dig more to see what's happening.

 Issue 756871  has been merged into this issue.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/59eb0b771d5401422576660be0c440c525d3fe76

commit 59eb0b771d5401422576660be0c440c525d3fe76
Author: Reza.Zakerinasab <zakerinasab@chromium.org>
Date: Mon Aug 28 08:27:35 2017

Fix regression in smoothness.tough_canvas_cases

This change fixes 12.8% regression in smoothness.tough_canvas_cases by
making sure that the color conversion code path in ImageData is invoked
only when necessary.

Bug:  756572 
Change-Id: I82ee267ad02085bbb5cc1c77ccec0087fa4ec6c6
Reviewed-on: https://chromium-review.googlesource.com/633909
Reviewed-by: Xida Chen <xidachen@chromium.org>
Reviewed-by: Justin Novosad <junov@chromium.org>
Commit-Queue: Mohammad Reza Zakerinasab <zakerinasab@chromium.org>
Cr-Commit-Position: refs/heads/master@{#497712}
[modify] https://crrev.com/59eb0b771d5401422576660be0c440c525d3fe76/third_party/WebKit/Source/modules/canvas2d/BaseRenderingContext2D.cpp