Add support for counting same-document AMP loads.

chrome/browser/page_load_metrics/observers/amp_page_load_metrics_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_PAGE_LOAD_METRICS_OBSERVERS_AMP_PAGE_LOAD_METRICS_OBSERVER_H_
 #define CHROME_BROWSER_PAGE_LOAD_METRICS_OBSERVERS_AMP_PAGE_LOAD_METRICS_OBSERVER_H_
 
 #include "base/macros.h"
 #include "chrome/browser/page_load_metrics/page_load_metrics_observer.h"
 
 namespace content {
 class NavigationHandle;
 }
 
 namespace page_load_metrics {
 struct PageLoadExtraInfo;
 struct PageLoadTiming;
 }
 
 // Observer responsible for recording page load metrics relevant to page served
 // from the AMP cache. When AMP pages are served in a same page navigation, UMA
 // is not recorded; this is typical for AMP pages navigated to from google.com.
 // Navigations to AMP pages from the google search app or directly to the amp
 // cache page will be tracked. Refreshing an AMP page served from google.com
 // will be tracked.
 class AMPPageLoadMetricsObserver
     : public page_load_metrics::PageLoadMetricsObserver {
  public:
   enum class AMPViewType {

[Ilya Sherman, 2017/05/17 19:26:43]

Please document that this enum is used to back an UMA histogram, and should
therefore be treated as append-only.

[Bryan McQuade, 2017/05/17 22:29:37]

Done, thanks!

     NONE,
     AMP_CACHE,
     GOOGLE_SEARCH_AMP_VIEWER,
     GOOGLE_NEWS_AMP_VIEWER,
+
+    // New values should be added before this final entry.
+    AMP_VIEW_TYPE_LAST
   };
 
   static AMPViewType GetAMPViewType(const GURL& url);
 
   AMPPageLoadMetricsObserver();
   ~AMPPageLoadMetricsObserver() override;
 
   // page_load_metrics::PageLoadMetricsObserver:
   ObservePolicy OnCommit(content::NavigationHandle* navigation_handle) override;
+  void OnCommitSameDocumentNavigation(
+      content::NavigationHandle* navigation_handle) override;
   void OnDomContentLoadedEventStart(
       const page_load_metrics::PageLoadTiming& timing,
       const page_load_metrics::PageLoadExtraInfo& info) override;
   void OnLoadEventStart(
       const page_load_metrics::PageLoadTiming& timing,
       const page_load_metrics::PageLoadExtraInfo& info) override;
   void OnFirstLayout(const page_load_metrics::PageLoadTiming& timing,
                      const page_load_metrics::PageLoadExtraInfo& info) override;
   void OnFirstContentfulPaintInPage(
       const page_load_metrics::PageLoadTiming& timing,
       const page_load_metrics::PageLoadExtraInfo& info) override;
   void OnParseStart(const page_load_metrics::PageLoadTiming& timing,
                     const page_load_metrics::PageLoadExtraInfo& info) override;
 
  private:
+  GURL current_url_;
   AMPViewType view_type_ = AMPViewType::NONE;
 
   DISALLOW_COPY_AND_ASSIGN(AMPPageLoadMetricsObserver);
 };
 
 #endif  // CHROME_BROWSER_PAGE_LOAD_METRICS_OBSERVERS_AMP_PAGE_LOAD_METRICS_OBSERVER_H_