25fdf10ad1
Add setBackgroundAlpha and use that to change the alpha of the
expanded view background and pointer.
Test: manual - have a bunch of bubbles, expand them, dismiss the
selected one
=> verify that the arrow is visible for the next bubble
- turn on home animation, swipe up to collapse a bubble
=> verify pointer looks fine
Bug: 234739591
Change-Id: If5823840d148e2031312c54eba9c0132b8aa3a4c