Add MediaRouter interface to browser's per-frame |renderer| capability

chrome/browser/chrome_content_browser_manifest_overlay.json

 {
   "name": "service:content_browser",
   "display_name": "Chrome",
   "interface_provider_specs": {
     "service_manager:connector": {
       "provides": {
         "renderer": [
           "autofill::mojom::AutofillDriver",
           "autofill::mojom::PasswordManagerDriver",
           "extensions::StashService",
@@ skipping 27 matching lines @@
     "navigation:frame": {
       "provides": {
         "renderer": [
           "autofill::mojom::AutofillDriver",
           "autofill::mojom::PasswordManagerDriver",
           "blink::mojom::ShareService",
           "dom_distiller::mojom::DistillabilityService",
           "dom_distiller::mojom::DistillerJavaScriptService",
           "extensions::KeepAlive",
           "extensions::mime_handler::MimeHandlerService",
+          "media_router::mojom::MediaRouter",
           "mojom::OmniboxPageHandler",
           "password_manager::mojom::CredentialManager",
           "translate::mojom::ContentTranslateDriver"
         ]
       }
     }
   }
 }