Implement scroll begin hints on Android for touch-action

ScrollBegin gesture events can now take a "deltaXhint" and "deltaYhint" that provide some information about the motion that triggered the start of a scroll.  This is used, for example, for touch-action: pan-x/pan-y support which needs to know what direction the user is scrolling as soon as the scroll starts.  Aura already populates these fields, and this CL adds Android support as well.

Also stop suppressing the sending of touch events to native code during a scroll.  This is a hold-over from when touchcancel logic was implemented in Java.

BUG=321643
R=jdduke@chromium.org

Review URL: https://codereview.chromium.org/121913002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@242730 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 242730