Grant content_browser access to all media interfaces

content/public/app/mojo/content_browser_manifest.json

 {
   "manifest_version": 1,
   "name": "exe:content_browser",
   "process-group": "browser",
   "display_name": "Content Browser",
   "capabilities": {
     // Remove this once http://crbug.com/632818 is fixed.
     "provided": {
       "all_interfaces": [ "*" ]
     },
@@ skipping 11 matching lines @@
           "shell:client_process",
           "shell:instance_name",
           "shell:user_id"
         ]
       },
       "mojo:file": {
         "interfaces": [
           "leveldb::mojom::LevelDBService",
           "user_service::UserService"
         ]
-      }
+      },
+      "mojo:media": { "classes": [ "all_interfaces" ] }
     }
   }
 }