This also moves the logic of inserting semaphores down into GrDrawingManager
and finishFlush on GrGpu. With it being on finishFlush, there should be no
issues when the DrawingManager starts respecting the proxy passed in assuming
it always calls finishFlush at the end (which it should).
Bug: skia:
Change-Id: I925c2a289dcbbb9159b9120878af1d34f21a2dc7
Reviewed-on: https://skia-review.googlesource.com/25641
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>
cd1416efbc