Be forgiving with accidental horizontal scroll

An accidental horizontal touch, due to vertical fling on the -1 screen
could lead to imperceptible change in zoom, and send a frame to client
composition. This CL adds extra padding to overlay scroll amount, to
avoid these accidental gestures.

Bug: 211245940
Test: https://ui.perfetto.dev/#!/viewer?trace_id=3260c116-c578-6dad-e047-0a327b7d346c
Change-Id: Id05e482c79c1dcc2e1ba73baf8a4a4101797bbd2