Implement SkiaRenderer::CopyDrawnRenderPass() for SkDDL and enable pixel tests.

Implement SkiaRenderer::CopyDrawnRenderPass() by posting a task to GPU main
thread to copy output from offscreen SkSurface for render passes or the
framebuffer SkSurface for the frame.

This CL also enable all existing pixel tests with SkaRenderer + SkDDL code path.


Bug: 824382
Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:mac_optional_gpu_tests_rel;luci.chromium.try:win_optional_gpu_tests_rel;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: I707d555c2973eb81294b29b813d4538ab671a3c0
Reviewed-on: https://chromium-review.googlesource.com/1089451
Reviewed-by: Ken Rockot <rockot@chromium.org>
Reviewed-by: Antoine Labour <piman@chromium.org>
Reviewed-by: danakj <danakj@chromium.org>
Reviewed-by: Robert Kroeger <rjkroege@chromium.org>
Commit-Queue: Peng Huang <penghuang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#568841}
17 files changed