Adds CastMetricsServiceClient to Chromecast shell.

Chromecast shell starts up MetricsService but reporting is largely
controlled in platform-specific ways. On the Chromecast dongle, this
occurs via the API that interfaces with the setup application.

R=lcwu@chromium.org,asvitkine@chromium.org,isherman@chromium.org,bryaneyler@chromium.org
BUG=400925

Review URL: https://codereview.chromium.org/482813004

Cr-Commit-Position: refs/heads/master@{#291588}
12 files changed