GitLab

With mus, OzonePlatform is created in the mus-ws thread, and it can be
accessed from the IO thread in GpuProcessHost. There is a race here,
since the IO thread and the mus-ws thread do not know about each other.
So, instead of immediately talking to the OzonePlatform instance from
GpuProcessHost, register a callback that gets run once the instance is
created and initialized. This way, with regular chrome (where
OzonePlatform is created on the UI thread), the callback is run
immediately. But with mus, it waits until the OzonePlatform instance is
available.

BUG=786453

Change-Id: I9c4553333ef29d5541cf3b65fed475c3cc7ef2db
Reviewed-on: https://chromium-review.googlesource.com/794103
Commit-Queue: Sadrul Chowdhury <sadrul@chromium.org>
Reviewed-by: Michael Spang <spang@chromium.org>
Reviewed-by: Antoine Labour <piman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#521353}