lazier and smaller conversation list progress bars

Avoid inflating refresh ProgressBars until they are actually needed.
ProgressBar inflation was instantiating all the drawable bitmaps, which
were 87KB on xhdpi * 9 assets (yikes). This was contributing to
excessive GCs, which slowed down list instantiation when coming back
from conversation view.

Also shrink the assets by removing the transparent bottom padding.

Bug: 8910559
Change-Id: If7bf3bb7df87646571b8e3aa371807b9b68d4656
30 files changed