Cherry Pick [Android] Properly handle cancelled scroll events

Cherry pick of https://codereview.chromium.org/27220002/

Bug: 10892868

Original description:
[Android] Properly handle cancelled scroll events

If the gesture handler receives an ACTION_CANCEL event during a scroll,
it should tell native to end scrolling.

Adds tests that the proper events are sent to native in both the normal
scroll sequence and the cancelled sequence.

BUG=b/10892868

Committed:
https://src.chromium.org/viewvc/chrome?view=rev&revision=228583

Change-Id: If69ceeb2ebb3e991d9b7ec9422ad514345a50e46
3 files changed