hwc: Add async method for refresh.

- Add method to call surfaceflinger invalidate
  asynchronously. This will allow hwc session
  to freely hold mutex while sending invalidate
  requests.
- Signal partial update control when a new draw
  cycle has been commited.

Change-Id: I04075ae7104ca87d7dac6de398fb4b6bc4408272
CRs-Fixed: 2037550
2 files changed