Collapsed DecoratedCustomView notifications show app name instead of title.

Previously, we never showed a title in the decorations, and
we still don't in the expanded decorations.  Rather than
making devleopers deal with the discrepancy, it's easier to
just show the app name for these views.  It makes them a
tad less desirable, but we could potentially give developers
a flag to opt into the title in the future.

Bug: 163626038
Bug: 173528244
Bug: 173742646
Test: manual
Change-Id: I8e5fe162c1ccdddcd39ea36f2b28fcc6aefd1f83