Remove unnecessary image downloading handler of notifications.

chrome/browser/background/background_contents_service.cc

Index: chrome/browser/background/background_contents_service.cc
diff --git a/chrome/browser/background/background_contents_service.cc b/chrome/browser/background/background_contents_service.cc
index fc49ec01499d39feeb1a1f2cc64eac005b612dfc..b0c954fc77b50e5ae0acab1d08c57b4b3b4e56c3 100644
--- a/chrome/browser/background/background_contents_service.cc
+++ b/chrome/browser/background/background_contents_service.cc
@@ -147,10 +147,6 @@ class CrashNotificationDelegate : public NotificationDelegate {
     return kNotificationPrefix + extension_id_;
   }
 
-  virtual content::WebContents* GetWebContents() const override {
-    return NULL;
-  }
-
  private:
   virtual ~CrashNotificationDelegate() {}