SkiaOutputSurface: Move GPU related code into SkiaOutputSurfaceImplOnGpu

This CL moves GPU related code in SkiaOutputSurfaceImpl into a new class
SkiaOutputSurfaceImplOnGpu. This new class is created, used and destroyed
on the GPU thread.

Bug: 824382
Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel
Change-Id: Ib5809b1b42b73e296344be4459058b52b36fee6a
Reviewed-on: https://chromium-review.googlesource.com/1017237
Commit-Queue: Peng Huang <penghuang@chromium.org>
Reviewed-by: Robert Kroeger <rjkroege@chromium.org>
Cr-Commit-Position: refs/heads/master@{#556851}
5 files changed