Annotate appropriate AudioRecordingDisclosureBar's methods with @UiThread

Adding @UiThread annotation to the methods in
AudioRecordingDisclosureBar.javva that should only be called on the
UI thread.

Change-Id: If37149b315c2044adfa09e32cd84a4c6a8c3f142
Bug: 134942150
Test: make, flash, rub audio recording app