Add mojo-based support for media device-change notifications.

content/public/app/mojo/content_renderer_manifest.json

 {
   "name": "service:content_renderer",
   "display_name": "Content (renderer process)",
   "interface_provider_specs": {
     "service_manager:connector": {
       "provides": {
         "browser": [
           "content::mojom::EmbeddedWorkerInstanceClient",
           "content::mojom::EmbeddedWorkerSetup",
           "content::mojom::FrameFactory",
           "content::mojom::RenderWidgetWindowTreeClientFactory",
           "IPC::mojom::ChannelBootstrap",
           "visitedlink::mojom::VisitedLinkNotificationSink",
           "web_cache::mojom::WebCache"
         ],
         "service_manager:service_factory": [
           "service_manager::mojom::ServiceFactory"
         ]
       },
       "requires": {
         "service:content_browser": [ "renderer" ],
         "service:ui": [ "ui:gpu_client" ]
       }
     },
     "navigation:frame": {
       "provides": {
         "browser": [
           "blink::mojom::AppBannerController",
-          "content::mojom::ImageDownloader"
+          "content::mojom::ImageDownloader",
+          "mojom::MediaDevicesListener"
         ]
       },
       "requires": {
         "service:content_browser": [ "renderer" ]
       }
     }
   }
 }