Fix here: https://codereview.chromium.org/2266883002

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/1329d0ac5e235bd6a94ef3ac22947ea6acf67363

commit 1329d0ac5e235bd6a94ef3ac22947ea6acf67363
Author: skyostil <skyostil@chromium.org>
Date: Mon Aug 22 18:04:48 2016

scheduler: Reset gesture state at start of a mouse drag

This patch fixes a bug where the scheduler did not reset gesture
tracking state when a new mouse drag gesture was started. This meant
that an unrelated gesture (e.g., a wheel scroll) could be used to
compute the policy for the mouse drag, potentially causing tasks
necessary to the gesture (e.g., timers) to get deferred.

We now consider a left button press as the start of a new gesture and
also keep track of which thread is processing the mouse move events
as we do with touch gestures.

BUG= 638212 

Review-Url: https://codereview.chromium.org/2266883002
Cr-Commit-Position: refs/heads/master@{#413475}

[modify] https://crrev.com/1329d0ac5e235bd6a94ef3ac22947ea6acf67363/third_party/WebKit/Source/platform/scheduler/renderer/renderer_scheduler_impl.cc
[modify] https://crrev.com/1329d0ac5e235bd6a94ef3ac22947ea6acf67363/third_party/WebKit/Source/platform/scheduler/renderer/renderer_scheduler_impl.h
[modify] https://crrev.com/1329d0ac5e235bd6a94ef3ac22947ea6acf67363/third_party/WebKit/Source/platform/scheduler/renderer/renderer_scheduler_impl_unittest.cc

We might want to backport this after a few days.

Requesting a merge to M53.

[Automated comment] Less than 2 weeks to go before stable on M53, manual review required.

Before we approve merge to M53, Could you please confirm whether this change is baked/verified in Canary and safe to merge? Please note that M53 is very close to Stable launch and bar is VERY high, we take this change ONLY if it is critical and safe.

Also is this change applicable to all OS or any specific OS?

On second thought, given M52 shipped with this bug and we haven't heard too many complaints (there have been some), let's ship this in M54 instead.

This is for all OSs (updated the flags).

Thank you, removing "Merge-Review-53" label based on comment #8.