Add a GestureConsumer callback to dispatching gesture events
and to get the targeted gesture event.

The touch_id_target_for_gestures table is no longer required
because the original targeted window will be available in the
callbacks.

BUG=568183

Review URL: https://codereview.chromium.org/1525233002

Cr-Commit-Position: refs/heads/master@{#366638}
17 files changed