GitLab

Converts to and from Cast API types. Also fixed a couple issues to
match the API between Cast and Extensions API.

Cast Extensions API is now fully redirected to Cast native APIs. Minus
the conversion of MediaStreamTrack.

BUG=301920

Review URL: https://codereview.chromium.org/47343005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@233366 0039d316-1c4b-4281-b951-d872f2087c98