Filter interception and handling of touch events.

Test: Execute repro steps described on bugs and ensure that Calculator
no longer crashes.

Fixes: 33396891
Fixes: 33430365

-DragLayout intercepting touch events while already in motion would
sometimes cause crashes.
-Remove unnecessary touchSlop check.
-Refactor DragLayout touch filtering to occur in tryCaptureView instead.

Change-Id: Ib4a90ab6fa54de33b9593fda6295a7be518a620b