Generalize the usage of referrer chain

chrome/browser/safe_browsing/safe_browsing_navigation_observer.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_SAFE_BROWSING_SAFE_BROWSING_NAVIGATION_OBSERVER_H_
 #define CHROME_BROWSER_SAFE_BROWSING_SAFE_BROWSING_NAVIGATION_OBSERVER_H_
 
 #include "base/supports_user_data.h"
 #include "content/public/browser/web_contents_observer.h"
 #include "url/gurl.h"
 
 namespace content {
 class NavigationHandle;
 }
 
 namespace safe_browsing {
 class SafeBrowsingNavigationObserverManager;
 
 // Struct to record the details of a navigation event for any frame.
-// This information will be used to fill |url_chain| field in safe browsing
-// download pings.
+// This information will be used to fill referrer chain info in various Safe
+// Browsing requests and reports.
 struct NavigationEvent {
   NavigationEvent();
   NavigationEvent(NavigationEvent&& nav_event);
   NavigationEvent& operator=(NavigationEvent&& nav_event);
   ~NavigationEvent();
 
   GURL source_url;  // URL that caused this navigation to occur.
                     // TODO(jialiul): source_url may be incorrect when
                     // navigation involves frames targeting each other.
                     // http://crbug.com/651895.
@@ skipping 89 matching lines @@
   bool has_user_gesture_;
 
   base::Time last_user_gesture_timestamp_;
 
   DISALLOW_COPY_AND_ASSIGN(SafeBrowsingNavigationObserver);
 };
 
 }  // namespace safe_browsing
 
 #endif  // CHROME_BROWSER_SAFE_BROWSING_SAFE_BROWSING_NAVIGATION_OBSERVER_H_