Prevents multi touch among TextView and handle reviews.

 - First touch on TextView blocks secondary touches on handles.
 - First touch on handles blocks later touches on TextView but doesn't block secondary touches on other handles.

Bug: 150995597
Test: manually tested & automation tests:
  atest FrameworksCoreTests:EditorCursorDragTest
  atest FrameworksCoreTests:TextViewActivityTest
Change-Id: I7717fc061fc81514fc1dad0d3acbc73e683516cf