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This implements (In Clank) the touch disposition handling method outlined here:
https://docs.google.com/a/chromium.org/document/d/176xYUC3WbiSl7qd08SBW4NiI4_gO0N4PN6tPAq49-68/edit?pli=1#bookmark=id.wu82d53abe2w

We also modify the way in which Aura handles touch move events to line up with the new way Android handles them. That is, consuming a touch move event prevents the next scroll update event, but does not prevent future scroll update events.

This change will have little impact until https://codereview.chromium.org/166923002/ has landed.

BUG=328503

Review URL: https://codereview.chromium.org/156783006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@251533 0039d316-1c4b-4281-b951-d872f2087c98