Revert "Revert "Revert "Add support for semaphores to be inserted on GrContext flush"""

This reverts commit 876aed8758b7109574999ffac43b1ea47f359bd7.

Reason for revert: the bots seem to be unhappily red with this CL

Original change's description:
> Revert "Revert "Add support for semaphores to be inserted on GrContext flush""
> 
> This reverts commit 8724b4609996eb6369b454611e31b065f3d8d2cf.
> 
> Reason for revert: Creating a test CL to see what happens on the bots
> 
> Original change's description:
> > Revert "Add support for semaphores to be inserted on GrContext flush"
> > 
> > This reverts commit cd1416efbc7af6f115dbaa09dce48e075d1d96ca.
> > 
> > Reason for revert: speculative, to try to fix roll see gpu_tests.pixel_integration_test.PixelIntegrationTest.Pixel_GpuRasterization_ConcavePaths
> > 
> > Original change's description:
> > > Add support for semaphores to be inserted on GrContext flush
> > > 
> > > 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>
> > 
> > TBR=egdaniel@google.com,bsalomon@google.com,robertphillips@google.com
> > 
> > Change-Id: I9c5b9cf8c060193e1861dbb8f0c10fb11dfb5249
> > No-Presubmit: true
> > No-Tree-Checks: true
> > No-Try: true
> > Bug: skia:
> > Reviewed-on: https://skia-review.googlesource.com/25980
> > Reviewed-by: Mike Reed <reed@google.com>
> > Commit-Queue: Mike Reed <reed@google.com>
> 
> TBR=egdaniel@google.com,bsalomon@google.com,robertphillips@google.com,reed@google.com
> 
> # Not skipping CQ checks because original CL landed > 1 day ago.
> 
> Bug: skia:
> Change-Id: I5edbeaa0769670ee58f362f0ccaa78319410aa6c
> Reviewed-on: https://skia-review.googlesource.com/26160
> Reviewed-by: Brian Salomon <bsalomon@google.com>
> Commit-Queue: Greg Daniel <egdaniel@google.com>

TBR=egdaniel@google.com,bsalomon@google.com,robertphillips@google.com,reed@google.com

Change-Id: I22fd6febafe70489a5fdb695c6f4263368eb423d
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: skia:
Reviewed-on: https://skia-review.googlesource.com/29422
Reviewed-by: Yuqian Li <liyuqian@google.com>
Commit-Queue: Yuqian Li <liyuqian@google.com>
25 files changed