Fix issues with swiping on some devices.

Some devices will send ACTION_MOVE events with the same coordinates as ACTION_DOWN. If so, we ignore them in order to correctly interpret the rest of the gesture.
Fix: 146472448
Test: Run talkback and swipe in all directions.
Test: atest AccessibilityGestureDetectorTest TouchExplorerTest GestureManifoldTest
Change-Id: I7c6ee32aa64cd9558afef4caf690f822f2541c5b