Add fling velocity updates from gesture curves.

As per crrev.com/13674008, WebGestureCurveTarget now supports fling velocity
notifications.  This patch hooks in the notifications from existing
WebGestureCurve implementations.

BUG=135975
NOTRY=true

Review URL: https://chromiumcodereview.appspot.com/14128010

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@197139 0039d316-1c4b-4281-b951-d872f2087c98
9 files changed