Replace old with new synthetic gesture framework.

- Remove current implementation of synthetic gestures.
- Rename temporarily named classes and files of new synthetic gesture framework
  (e.g. SyntheticGestureNew -> SyntheticGesture).
- Link up new implementation in browser and renderer.
- Hook up synthetic gesture controller to input flushing in RWHI.
- Update JavaScript front-end and Telemetry.

BUG=297980

Review URL: https://codereview.chromium.org/62443007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@236254 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 236254