Always do a HIT_TEST

 Bug: 6490959
 The issue here is that if the page calls preventDefault on a
 touchstart handler WebViewClassic will not do a HIT_TEST as it
 doesn't get the ACTION_DOWN. This means that the mouse is in the
 wrong position when the click ultimately fires.

 This changes it so that WebViewInputDispatcher will always do a
 HIT_TEST at the start of a touch stream, which ensures that the
 mouse is positioned correctly.

Change-Id: I1aaca7692e2c7aeedeb21fa3592cd4cb3223ea25