Ignore blocked-on-sf time for ADPF

Subtract out time spent blocked in dequeueBuffer. Also subtract out any
time UI spents waiting on render thread while render thread is blocked
dequeueBuffer, though this calculation is fairly crude.

Test: Checked bouncyball returns reasonable-ish numbers even when HWUI
      is ahead of surface flinger
Bug: 187556381
Change-Id: I368c446d93990ff8b7b645e30509405ba799c79c