Pass origin to StartObservingMediaSinks.

chrome/browser/media/router/media_source_helper.h

Index: chrome/browser/media/router/media_source_helper.h
diff --git a/chrome/browser/media/router/media_source_helper.h b/chrome/browser/media/router/media_source_helper.h
index 0e2822a99025ea979ed7e9520a0385cce6e02f8e..d3b8bb0989f8ae52fd5db6699895f377d84a7cc9 100644
--- a/chrome/browser/media/router/media_source_helper.h
+++ b/chrome/browser/media/router/media_source_helper.h
@@ -8,6 +8,7 @@
 #include <string>
 
 #include "chrome/browser/media/router/media_source.h"
+#include "url/gurl.h"
 
 namespace media_router {
 
@@ -18,6 +19,8 @@ MediaSource MediaSourceForDesktop();
 MediaSource MediaSourceForCastApp(const std::string& app_id);
 MediaSource MediaSourceForPresentationUrl(const std::string& presentation_url);
 
+GURL OriginForDesktop();
+
 // Returns true if |source| outputs its content via mirroring.
 bool IsDesktopMirroringMediaSource(const MediaSource& source);
 bool IsTabMirroringMediaSource(const MediaSource& source);