bsep@, looks like your CL https://codereview.chromium.org/1911973002 is culprit. Can you look into it?

 Issue 614620  has been merged into this issue.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/57decb6dda19498ceec3b3cbdb9d6c6fd0fed001

commit 57decb6dda19498ceec3b3cbdb9d6c6fd0fed001
Author: bsep <bsep@chromium.org>
Date: Wed May 25 22:33:51 2016

Fix scrollbar buttons on ChromeOS.

Scrollbar buttons aren't supposed to draw on ChromeOS, so they need to
return a size of 0.

BUG= 613668 

Review-Url: https://codereview.chromium.org/2006643004
Cr-Commit-Position: refs/heads/master@{#396012}

[modify] https://crrev.com/57decb6dda19498ceec3b3cbdb9d6c6fd0fed001/third_party/WebKit/Source/platform/scroll/ScrollbarThemeAura.cpp
[modify] https://crrev.com/57decb6dda19498ceec3b3cbdb9d6c6fd0fed001/third_party/WebKit/Source/platform/scroll/ScrollbarThemeAura.h
[modify] https://crrev.com/57decb6dda19498ceec3b3cbdb9d6c6fd0fed001/third_party/WebKit/Source/platform/scroll/ScrollbarThemeAuraTest.cpp

this needs to be merged to 52.

Your change meets the bar and is auto-approved for M52 (branch: 2743)

This issue has been approved for a merge. Please merge the fix to any appropriate branches as soon as possible!

If all merges have been completed, please remove any remaining Merge-Approved labels from this issue.

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This issue has been approved for a merge. Please merge the fix to any appropriate branches as soon as possible!

If all merges have been completed, please remove any remaining Merge-Approved labels from this issue.

Thanks for your time! To disable nags, add the Disable-Nags label.

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

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/ee145b086b49d2cf71b915f5dc6e6e806edd613b

commit ee145b086b49d2cf71b915f5dc6e6e806edd613b
Author: Scott Graham <scottmg@chromium.org>
Date: Mon Jun 06 20:15:53 2016

Fix scrollbar buttons on ChromeOS.

Scrollbar buttons aren't supposed to draw on ChromeOS, so they need to
return a size of 0.

BUG= 613668 

Review-Url: https://codereview.chromium.org/2006643004
Cr-Commit-Position: refs/heads/master@{#396012}
(cherry picked from commit 57decb6dda19498ceec3b3cbdb9d6c6fd0fed001)

Review URL: https://codereview.chromium.org/2042023002 .

Cr-Commit-Position: refs/branch-heads/2743@{#247}
Cr-Branched-From: 2b3ae3b8090361f8af5a611712fc1a5ab2de53cb-refs/heads/master@{#394939}

[modify] https://crrev.com/ee145b086b49d2cf71b915f5dc6e6e806edd613b/third_party/WebKit/Source/platform/scroll/ScrollbarThemeAura.cpp
[modify] https://crrev.com/ee145b086b49d2cf71b915f5dc6e6e806edd613b/third_party/WebKit/Source/platform/scroll/ScrollbarThemeAura.h
[modify] https://crrev.com/ee145b086b49d2cf71b915f5dc6e6e806edd613b/third_party/WebKit/Source/platform/scroll/ScrollbarThemeAuraTest.cpp

Chrome OS 53.0.2764.0/8452.0.0