12/ Clean up some ActivityInterface calls

- Require users of the activity interface to go through the interface to
  get the raw activity
- Remove calls that pass in the activity since the interface already can
  get the reference to it internally (and the interface always has the
  reference before the caller)

Bug: 141886704

Change-Id: I13e52caba593db918e8a7764c751044142fe7ece
Signed-off-by: Winson Chung <winsonc@google.com>