Fix the exiting window still can receive touch.

If a window request to exit, but the animation haven't started yet.
It should not receive any touch event for this moment. Or it can't be
expected that sent the touch events to the invisible view during
animation.

Bug: 117801507
Test: Open Settings, enter sub setting page, Tapping back and tap top
      right corner to see if any Support page lunches in Chrome.

Change-Id: I8f6bc46a8d1fded277605f07cacf057715aed1c0