Enable backpressure for client composition to avoid jank due to
HWC queue stuffing.

Bug: 146129613
Test: 1. Open Camera
      2. Swipe vertically to go back to home screen
      3. Measure the "FrameMissed" count from systrace result

Change-Id: Icd7a92bda5c874dd72d6da4ae991919cbc5b79b1