Flush TouchPad generated GestureScrollEnd immediately

Similar to crbug.com/704732, TouchPad generated gesture events will also
get delayed to next frame. (assuming MouseWheel events are always
blocking)

We want flush the queue to avoid regression on
'first_gesture_scroll_update_latency'.

Bug: 737547
Change-Id: I43289864a3e8c528ce57c38dac7de529de8cd0f0
Reviewed-on: https://chromium-review.googlesource.com/557463
Commit-Queue: Chong Zhang <chongz@chromium.org>
Reviewed-by: Timothy Dresser <tdresser@chromium.org>
Cr-Commit-Position: refs/heads/master@{#484157}
2 files changed