GitLab

GetRootWindow can return null but ScheduleFlingProgress doesn't check
for it.

Bug: 855045
Change-Id: Ib82b8169d74efc02800bd7b975f111f653bbadc3
Reviewed-on: https://chromium-review.googlesource.com/1110260
Commit-Queue: Saman Sami <samans@chromium.org>
Reviewed-by: Timothy Dresser <tdresser@chromium.org>
Cr-Commit-Position: refs/heads/master@{#569313}