Remove unnecessary image downloading handler of notifications.

chrome/browser/ui/views/message_center/web_notification_tray_browsertest.cc

Index: chrome/browser/ui/views/message_center/web_notification_tray_browsertest.cc
diff --git a/chrome/browser/ui/views/message_center/web_notification_tray_browsertest.cc b/chrome/browser/ui/views/message_center/web_notification_tray_browsertest.cc
index e2d1c6d24875160c85df784035f5a9d08f403dd4..73b7f0ebdcba27a4b4a0a0397056c8d71869176b 100644
--- a/chrome/browser/ui/views/message_center/web_notification_tray_browsertest.cc
+++ b/chrome/browser/ui/views/message_center/web_notification_tray_browsertest.cc
@@ -52,9 +52,6 @@ class WebNotificationTrayTest : public InProcessBrowserTest {
     virtual void Close(bool by_user) override {}
     virtual void Click() override {}
     virtual std::string id() const override { return id_; }
-    virtual content::WebContents* GetWebContents() const override {
-      return NULL;
-    }
 
    private:
     virtual ~TestNotificationDelegate() {}