Remove unnecessary image downloading handler of notifications.

chrome/browser/status_icons/desktop_notification_balloon.cc

Index: chrome/browser/status_icons/desktop_notification_balloon.cc
diff --git a/chrome/browser/status_icons/desktop_notification_balloon.cc b/chrome/browser/status_icons/desktop_notification_balloon.cc
index 76e5f5642edfce644ca816765862684fec597dbe..528df5822670e56c76e122cc7b9793afec88a0e6 100644
--- a/chrome/browser/status_icons/desktop_notification_balloon.cc
+++ b/chrome/browser/status_icons/desktop_notification_balloon.cc
@@ -49,9 +49,6 @@ class DummyNotificationDelegate : public NotificationDelegate {
   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 ~DummyNotificationDelegate() {}