GitLab

Added Fling Bubbling browsertests.

The tests were initially landed in the following cl:
https://chromium-review.googlesource.com/c/chromium/src/+/1278963

The logic of the cl is re-landed in a separate cl(r599781) to give it
more time to bake. This cl re-lands the browser tests after applying
the following changes:

1- Addressed renaming nit.
2- Used MainThreadFrameObserver to make sure that compositor is synced
after scrolling on main thread.

Bug: 894703
Change-Id: I25d6dbf7f216bbedecb6673d6c2819dcd1d82d55
Reviewed-on: https://chromium-review.googlesource.com/c/1286875Reviewed-by: Charlie Reis <creis@chromium.org>
Reviewed-by: Kevin McNee <mcnee@chromium.org>
Commit-Queue: Sahel Sharify <sahel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#600509}