[Android] Harden eager gesture recognition

With the landing of eager gesture recognition, several corner cases in touch
handling have been uncovered that went previously untested.  Add additional
guards to both ContentViewGestureHandler and TouchDispositionGestureFilter to
properly handle these cases.

BUG=340600,341404

Review URL: https://codereview.chromium.org/143663005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@249727 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 249727