Add flag AMOTION_EVENT_FLAG_IS_GENERATED_GESTURE to Input.h

Since there is no support for touchpad gestures yet, the gestures are
sent as MotionEvents with the flag:
AMOTION_EVENT_FLAG_IS_GENERATED_GESTURE

This flag is already present in java as:
MotionEvent.FLAG_IS_GENERATED_GESTURE

This change adds the flag to Input.h.

Bug: 119265089
Test: none
Change-Id: Ide0cc41d3f44a8694fa02faa0337eb2cf72de6f2
diff --git a/include/input/Input.h b/include/input/Input.h
index d35354b..cc45aef 100644
--- a/include/input/Input.h
+++ b/include/input/Input.h
@@ -59,6 +59,12 @@
      */
     AMOTION_EVENT_FLAG_WINDOW_IS_PARTIALLY_OBSCURED = 0x2,
 
+    /**
+     * This flag indicates that the event has been generated by a gesture generator. It
+     * provides a hint to the GestureDetector to not apply any touch slop.
+     */
+    AMOTION_EVENT_FLAG_IS_GENERATED_GESTURE = 0x8,
+
     /* Motion event is inconsistent with previously sent motion events. */
     AMOTION_EVENT_FLAG_TAINTED = 0x80000000,
 };