[Device Discovery] Make DialRegistry a Singleton

chrome/browser/extensions/api/dial/dial_api.h

Index: chrome/browser/extensions/api/dial/dial_api.h
diff --git a/chrome/browser/extensions/api/dial/dial_api.h b/chrome/browser/extensions/api/dial/dial_api.h
index 7ee0d14e3ee811eeac88313aadc7c46fb2f4cd27..e9fb6ccd1a04125ee1b36f8037c303b56f1c220c 100644
--- a/chrome/browser/extensions/api/dial/dial_api.h
+++ b/chrome/browser/extensions/api/dial/dial_api.h
@@ -92,8 +92,9 @@ class DialAPI : public RefcountedKeyedService,
 
   Profile* profile_;
 
-  // Created lazily on first access on the IO thread.
-  std::unique_ptr<media_router::DialRegistry> dial_registry_;
+  // Created lazily on first access on the IO thread. Does not take ownership of
+  // |dial_registry_|.
+  media_router::DialRegistry* dial_registry_;
 
   // Device data for testing.
   std::unique_ptr<media_router::DialDeviceData> test_device_data_;