content: convert zoom notifications to observer usage

chrome/browser/ui/zoom/zoom_controller_unittest.cc

Index: chrome/browser/ui/zoom/zoom_controller_unittest.cc
diff --git a/chrome/browser/ui/zoom/zoom_controller_unittest.cc b/chrome/browser/ui/zoom/zoom_controller_unittest.cc
index cc5be54baac2a7ff5e1c83143e8901c4e9beae37..f96cfb7bb98a3cd16a023bac6b4dff1a15286681 100644
--- a/chrome/browser/ui/zoom/zoom_controller_unittest.cc
+++ b/chrome/browser/ui/zoom/zoom_controller_unittest.cc
@@ -14,9 +14,6 @@
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/host_zoom_map.h"
 #include "content/public/browser/navigation_details.h"
-#include "content/public/browser/notification_details.h"
-#include "content/public/browser/notification_source.h"
-#include "content/public/browser/notification_types.h"
 #include "content/public/common/frame_navigate_params.h"
 #include "content/public/test/test_browser_thread.h"
 #include "content/public/test/test_utils.h"
@@ -71,11 +68,5 @@ TEST_F(ZoomControllerTest, Observe) {
       content::HostZoomMap::GetForBrowserContext(
           web_contents()->GetBrowserContext());
 
-  content::WindowedNotificationObserver notification_observer(
-      content::NOTIFICATION_ZOOM_LEVEL_CHANGED,
-      content::NotificationService::AllSources());
-
   host_zoom_map->SetZoomLevel(std::string(), 110.0f);
-
-  notification_observer.Wait();
 }