Fix a param signature in BrowserPluginGuest.

content/browser/browser_plugin/browser_plugin_guest.h

Index: content/browser/browser_plugin/browser_plugin_guest.h
diff --git a/content/browser/browser_plugin/browser_plugin_guest.h b/content/browser/browser_plugin/browser_plugin_guest.h
index 2fb3bbc2c10e4717b4145f92582446dfcdc33a66..1b480e6acfee67497a9939acae438476fbb43a7c 100644
--- a/content/browser/browser_plugin/browser_plugin_guest.h
+++ b/content/browser/browser_plugin/browser_plugin_guest.h
@@ -218,7 +218,7 @@ class CONTENT_EXPORT BrowserPluginGuest : public NotificationObserver,
   // Requests geolocation permission through embedder js api.
   void AskEmbedderForGeolocationPermission(int bridge_id,
                                            const GURL& requesting_frame,
-                                           GeolocationCallback callback);
+                                           const GeolocationCallback& callback);
   // Cancels pending geolocation request.
   void CancelGeolocationRequest(int bridge_id);
   // Embedder sets permission to allow or deny geolocation request.