Since the button for clearing recent conversations may still
exist after the user triggers the button since some of the
conversations might not be removable
Test: manual with talkback
Fixes: 185433664
Change-Id: Id58d76237643e4e206ea6d551cdf7dd9f5742282
- Don't show the button if nothing is clearable
- Optimistically remove preferences on pressing clear since the actualy
clear action is asynchronous
Test: RoboTests
Fixes: 178765511
Change-Id: Ic305d4d199b149078ea52a614cb93cebe55cd245