Separate updating views from deriving state

The benefit is that icon colors and icon scaling can be performed on a
background thread and then all of the views updated on the main thread.

Bug: 150454272
Test: atest KeyguardMediaPlayerTest.kt
Test: manual - play music and look at lock screen controls
Change-Id: I2423233f1ddeb081ab420053964c2b1cb2185514
3 files changed