Create a dismiss zone for bubble bar dragging

Create an area around the dismiss circle where the bubble bar can't be
dragged to the other side.
Avoids user accidentally moving the bar to the other side when getting
close to the dismiss target.

Bug: 313661121
Test: manual, drag the expanded view around the dismiss target, check
  that the bar is not moved to the other side, when moving farther, bar
  is moved to the other side
Change-Id: I43b3aa07316a9ded050d678b067c2684397eda98