gpu: Share GrContext between RasterDecoders for OOP raster.

Use a common GrContext across all RasterDecoders. This ensures that we
get a unified GrProgramCache for compiled shaders.

[email protected], [email protected]

Bug: 854416
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
Change-Id: I653486d2a20f4bb0112c6cfe66f3922c222ad338
Reviewed-on: https://chromium-review.googlesource.com/1114287
Commit-Queue: Khushal <[email protected]>
Reviewed-by: Antoine Labour <[email protected]>
Reviewed-by: Eric Karl <[email protected]>
Cr-Commit-Position: refs/heads/master@{#572377}
15 files changed