gpu: Allow empty sync tokens in mailboxes.
ResourceProvider doesn't allow an empty sync token to be set on
mailboxes even if that's intended. Furthermore, sync token verification
doesn't work with empty sync tokens so they'd trigger dchecks in the IPC
layer. This CL fixes both these issues. This is intended to be used by
upcoming mojo VDA which runs command in the GPU process before returning
a mailbox to the client. In this case an empty sync token makes sense
because there is nothing to wait for.
R=piman
BUG=522298
Cq-Include-Trybots: master.tryserver.blink:linux_trusty_blink_rel;master.tryserver.chromium.android:android_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel
Change-Id: Id9b120d8303e5f32ca63d909d8d2d2b945145da6
Reviewed-on: https://chromium-review.googlesource.com/548973
Commit-Queue: Sunny Sachanandani <sunnyps@chromium.org>
Reviewed-by: Antoine Labour <piman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#482759}4 files changed
