Add support for counting same-document AMP loads.

chrome/browser/page_load_metrics/page_load_tracker.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_PAGE_LOAD_METRICS_PAGE_LOAD_TRACKER_H_
 #define CHROME_BROWSER_PAGE_LOAD_METRICS_PAGE_LOAD_TRACKER_H_
 
 #include <memory>
 #include <vector>
 
@@ skipping 189 matching lines @@
                   const GURL& currently_committed_url,
                   content::NavigationHandle* navigation_handle,
                   UserInitiatedInfo user_initiated_info,
                   int aborted_chain_size,
                   int aborted_chain_size_same_url);
   ~PageLoadTracker();
   void Redirect(content::NavigationHandle* navigation_handle);
   void WillProcessNavigationResponse(
       content::NavigationHandle* navigation_handle);
   void Commit(content::NavigationHandle* navigation_handle);
+  void DidCommitSameDocumentNavigation(
+      content::NavigationHandle* navigation_handle);
   void DidFinishSubFrameNavigation(
       content::NavigationHandle* navigation_handle);
   void FailedProvisionalLoad(content::NavigationHandle* navigation_handle,
                              base::TimeTicks failed_load_time);
   void WebContentsHidden();
   void WebContentsShown();
 
   void OnInputEvent(const blink::WebInputEvent& event);
 
   // Flush any buffered metrics, as part of the metrics subsystem persisting
@@ skipping 212 matching lines @@
   // Navigation start offsets for the most recently committed document in each
   // frame.
   std::map<FrameTreeNodeId, base::TimeDelta> subframe_navigation_start_offset_;
 
   DISALLOW_COPY_AND_ASSIGN(PageLoadTracker);
 };
 
 }  // namespace page_load_metrics
 
 #endif  // CHROME_BROWSER_PAGE_LOAD_METRICS_PAGE_LOAD_TRACKER_H_