Patch is at https://chromium-review.googlesource.com/644855

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/c4ab70eec883c83d63c8b9a7141a1bab35c0dc37

commit c4ab70eec883c83d63c8b9a7141a1bab35c0dc37
Author: Eugene Girard <girard@chromium.org>
Date: Fri Sep 15 18:15:18 2017

Refactor (eliminate) MaybeReleaseNumber

In a recent patch I added the function SequentialIDGenerator::MaybeReleaseNumber which
protected against two threads assigning and releasing the same number. During review,
it was suggested we could get rid of ReleaseNumber since all clients had been migrated
to MaybeReleaseNumber.

This patch cleans up the two functions, leaving only one. 

Bug:  759003 
Change-Id: I7863162e7abcecfa5e5196f2dec5825e977182f2
Reviewed-on: https://chromium-review.googlesource.com/644855
Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Commit-Queue: Eugene Girard <girard@chromium.org>
Cr-Commit-Position: refs/heads/master@{#502306}
[modify] https://crrev.com/c4ab70eec883c83d63c8b9a7141a1bab35c0dc37/ui/events/devices/x11/touch_factory_x11.cc
[modify] https://crrev.com/c4ab70eec883c83d63c8b9a7141a1bab35c0dc37/ui/events/ozone/evdev/event_factory_evdev.cc
[modify] https://crrev.com/c4ab70eec883c83d63c8b9a7141a1bab35c0dc37/ui/gfx/sequential_id_generator.cc
[modify] https://crrev.com/c4ab70eec883c83d63c8b9a7141a1bab35c0dc37/ui/gfx/sequential_id_generator.h
[modify] https://crrev.com/c4ab70eec883c83d63c8b9a7141a1bab35c0dc37/ui/gfx/sequential_id_generator_unittest.cc
[modify] https://crrev.com/c4ab70eec883c83d63c8b9a7141a1bab35c0dc37/ui/views/win/hwnd_message_handler.cc
[modify] https://crrev.com/c4ab70eec883c83d63c8b9a7141a1bab35c0dc37/ui/views/win/pen_event_processor.cc