Move stroke buffer and gesture recognition out of TouchExplorer.

This also adds a return value to the callbacks on
AccessibilityGestureDetector.Listener, so that the listener can indicate if the
event has been consumed, and processing should be halted.

b/25021896

Change-Id: If4d366ff207c1cebd0e3f7dab5f27a2037ddb510
2 files changed