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When using SurfaceControl after surface has been returned we need to
wait until fence provided by system will be signaled. When using GL
for compositing, this is implemented as importing provided file
descriptor as egl fence and issue ServerWait().

GLRenderer does it when we get surface back. With SkiaRenderer it
happens on next BeginWrite for the SharedImage. Import is expensive
operation and BeginWrite is on critical path.

This CL moves import to EndOverlayAccess as we will do it anyway.
Then at BeginWrite time we only issue ServerWait().

In local tests with scrolling simple page it saves 200us in
DrawToSwapUs metric.

Change-Id: I6efb2783d0e287dc5e4fbb5707c507328e75a32f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2019607Reviewed-by: Jonathan Backer <backer@chromium.org>
Reviewed-by: Ken Buchanan <kenrb@chromium.org>
Commit-Queue: Vasiliy Telezhnikov <vasilyt@chromium.org>
Cr-Commit-Position: refs/heads/master@{#735577}