GitLab

Add OnStatisticsUpdate and OnWaitingForDecryptionKey to
mojom::RendererClient, and call these callbacks from
MojoRendererService. These are needed for Cast Apps like Netflix that
depend on decoding statistics from the media pipeline.

BUG=585287
BUG= internal b/29390639

Review-Url: https://codereview.chromium.org/2101043003
Cr-Commit-Position: refs/heads/master@{#404486}