Expose a method in VariationsService to trigger a seed fetch.

On mobile this will launch a (slightly delayed) request, iff the seed hasn't been refreshed in the past 5 hours. On desktop this will use the currently existing method on desktop, which does not do that check.

BUG=321379

Review URL: https://codereview.chromium.org/147723010

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@251532 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 251532
Consuming a touch move prevents only the next scroll update.

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
SVN changes up to revision 251533
Removed unused dependency.

BUG=

Review URL: https://codereview.chromium.org/167453002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@251534 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 251534