Use GrSemaphore rather than GrFence for external texture data

BUG=skia:

Change-Id: I0d23eb9dcf5c01c71d3571ef97690af68b900807
Reviewed-on: https://skia-review.googlesource.com/9141
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
10 files changed