Remove unnecessary image downloading handler of notifications.

chrome/browser/notifications/notification_test_util.cc

Index: chrome/browser/notifications/notification_test_util.cc
diff --git a/chrome/browser/notifications/notification_test_util.cc b/chrome/browser/notifications/notification_test_util.cc
index 71a0d064942400e73f028d2ec911de1d94e5408f..fa8bdd4ab1ec7444c2a5d4f1aa6666601704a9a0 100644
--- a/chrome/browser/notifications/notification_test_util.cc
+++ b/chrome/browser/notifications/notification_test_util.cc
@@ -11,10 +11,6 @@ MockNotificationDelegate::~MockNotificationDelegate() {}
 
 std::string MockNotificationDelegate::id() const { return id_; }
 
-content::WebContents* MockNotificationDelegate::GetWebContents() const {
-  return NULL;
-}
-
 // TODO(peter): |notification_| should be initialized with the correct origin.
 StubNotificationUIManager::StubNotificationUIManager(const GURL& welcome_origin)
     : notification_(GURL(),