GitLab

This CL turns the "Compositor Threaded Scrollbar Scrolling" on by
default in master. The details about this feature can be found in
the following links:

Design doc: https://docs.google.com/document/d/1JqykSXnCkqwA1E3bUhhIi-IgEvM9HZdKtIu_S4Ncm6o
Demo page: https://rahul8805.github.io/DemoPages/BouncyMoon.html
Lightning talk: https://www.youtube.com/watch?v=FOCHCuGA_MA&t=1150s
input-dev thread: https://groups.google.com/a/chromium.org/forum/#!topic/input-dev/6ACOSDoAik4

Bug: 148501
Change-Id: Iec2e4de5c79e94815629be37c5bbe4ed435e106b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2048418Reviewed-by: David Bokan <bokan@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Rahul Arakeri <arakeri@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#745266}