Add PageLoad.* metrics for Offline Previews

chrome/browser/android/offline_pages/offline_page_tab_helper.h

Index: chrome/browser/android/offline_pages/offline_page_tab_helper.h
diff --git a/chrome/browser/android/offline_pages/offline_page_tab_helper.h b/chrome/browser/android/offline_pages/offline_page_tab_helper.h
index 6bf460b072ceeafb3ef5662e8ecdf2edb6552e56..56ece35f7cca566815b59a5c37bf603804f80970 100644
--- a/chrome/browser/android/offline_pages/offline_page_tab_helper.h
+++ b/chrome/browser/android/offline_pages/offline_page_tab_helper.h
@@ -61,21 +61,24 @@ class OfflinePageTabHelper :
     // Prohibitively slow means that the NetworkQualityEstimator reported a
     // connection slow enough to warrant showing an offline page if available.
     REDIRECTED_ON_PROHIBITIVELY_SLOW_NETWORK = 10,
     PAGE_NOT_FOUND_ON_PROHIBITIVELY_SLOW_NETWORK = 11,
     PAGE_NOT_FRESH_ON_PROHIBITIVELY_SLOW_NETWORK = 12,
     REDIRECT_RESULT_MAX,
   };
 
   ~OfflinePageTabHelper() override;
 
-  const OfflinePageItem* offline_page() { return offline_page_.get(); }
+  const OfflinePageItem* offline_page() const { return offline_page_.get(); }
+
+  // Whether the page is an offline preview.
+  bool is_offline_preview() const { return is_offline_preview_; }
 
  private:
   friend class content::WebContentsUserData<OfflinePageTabHelper>;
   friend class OfflinePageTabHelperTest;
   FRIEND_TEST_ALL_PREFIXES(OfflinePageTabHelperTest,
                            NewNavigationCancelsPendingRedirects);
 
   explicit OfflinePageTabHelper(content::WebContents* web_contents);
 
   void SetDelegateForTesting(std::unique_ptr<Delegate> delegate);
@@ -110,18 +113,22 @@ class OfflinePageTabHelper :
   bool IsInRedirectLoop(const GURL& to_url) const;
 
   void ReportRedirectResultUMA(RedirectResult result);
 
   // Iff the tab we are associated with is redirected to an offline page,
   // |offline_page_| will be non-null.  This can be used to synchronously ask
   // about the offline state of the current web contents.
   std::unique_ptr<OfflinePageItem> offline_page_;
   std::unique_ptr<Delegate> delegate_;
 
+  // Whether the page is an offline preview. Offline page previews are shown
+  // when a user's effective connection type is prohibitively slow.
+  bool is_offline_preview_;
+
   base::WeakPtrFactory<OfflinePageTabHelper> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(OfflinePageTabHelper);
 };
 
 }  // namespace offline_pages
 
 #endif  // CHROME_BROWSER_ANDROID_OFFLINE_PAGES_OFFLINE_PAGE_TAB_HELPER_H_