Add TransactionCompleteCallback

Allow users of BlastBufferQueue to register for transaction complete for
a particular frame number. This will allow VRI to know when a
transaction was applied so it can continue rendering after a relayout.

Test: Split screen with blast sync
Bug: 167202096
Change-Id: If0bb5b496a462ba486b05b0ddc35bff66eb29e1a
2 files changed