Make the handwriting surface NOT_TOUCHABLE

Looks like we forgot to do it. INPUT_FEATURE_INTERCEPTS_STYLUS is meant
to be used in conjunction with FLAG_NOT_TOUCHABLE. Without the latter,
the window will still receive all pointer events.

Bug: 210039666
Test: None
Change-Id: I724da1432dd3f38b82676b5ca924040f4aa78a94
1 file changed