[Chromecast] Raises CastService creation to CastContentBrowserClient.
This is a first step toward resolving the chromecast/service/ --> content/
dependency by removing the link-time creation path in CastService.
Also, removes some code that has become dead via refactoring across the
internal/external repository boundary.
Review URL: https://codereview.chromium.org/1327723002
15 files changed