Implement setSinkId() for media elements without src.

content/renderer/render_frame_impl.h

Index: content/renderer/render_frame_impl.h
diff --git a/content/renderer/render_frame_impl.h b/content/renderer/render_frame_impl.h
index d850ac99fc589ece0f59d3c28e3d2c58ef4818fa..31b19141d9f14d938e7ae1cee17ba155840fab5c 100644
--- a/content/renderer/render_frame_impl.h
+++ b/content/renderer/render_frame_impl.h
@@ -884,6 +884,12 @@ class CONTENT_EXPORT RenderFrameImpl
   // ServiceProvider.
   mojo::ServiceProviderPtr ConnectToApplication(const GURL& url);
 
+  // Checks that |sink_id| exists and is authorized to be used on
+  // |security_origin|.
+  void checkAudioSink(const blink::WebString& sink_id,
+                      const blink::WebSecurityOrigin& security_origin,
+                      blink::WebSetSinkIdCallbacks* callback) override;
+
   // Stores the WebLocalFrame we are associated with.  This is null from the
   // constructor until SetWebFrame is called, and it is null after
   // frameDetached is called until destruction (which is asynchronous in the