Reload offline version on load failure

ios/chrome/browser/reading_list/reading_list_web_state_observer.h

Index: ios/chrome/browser/reading_list/reading_list_web_state_observer.h
diff --git a/ios/chrome/browser/reading_list/reading_list_web_state_observer.h b/ios/chrome/browser/reading_list/reading_list_web_state_observer.h
index 47fcfb6f9aa4c0075e442c5ac0b852bb6dfc376f..1c16afed1ccfe4624596a719084ee81853c1588f 100644
--- a/ios/chrome/browser/reading_list/reading_list_web_state_observer.h
+++ b/ios/chrome/browser/reading_list/reading_list_web_state_observer.h
@@ -12,6 +12,10 @@
 
 class ReadingListModel;
 
+namespace web {
+class NavigationItem;
+}
+
 // Observes the loading of pages coming from the reading list, determines
 // whether loading an offline version of the page is needed, and actually
 // trigger the loading of the offline page (if possible).
@@ -23,34 +27,44 @@ class ReadingListWebStateObserver : public web::WebStateObserver {
 
   ~ReadingListWebStateObserver() override;
 
-  // Starts checking that the current navigation is loading quickly enough [1].
-  // If not, starts to load a distilled version of the page (if there is any).
-  // If that same WebStateObserver was already checking that a page was loading
-  // quickly enough, stops checking the loading of that page.
-  // [1] A page loading quickly enough is a page that has loaded 15% within
-  // 1 second.
-  void StartCheckingProgress(const GURL& pending_url);
-
  private:
   ReadingListWebStateObserver(web::WebState* web_state,
                               ReadingListModel* reading_list_model);
 
-  // Looks at the loading percentage. If less than 15%, attemps to load the
-  // offline version of that page.
+  // Looks at the loading percentage. If less than 25% * time, attemps to load
+  // the offline version of that page.
+  // |time| is the number of seconds since |StartCheckingProgress| was called.
   void VerifyIfReadingListEntryStartedLoading();
 
   friend class ReadingListWebStateObserverUserDataWrapper;
 
-  // Stop checking the loading of the |pending_url_|.
+  // Stops checking the loading of the |pending_url_|.
   // The WebState will still be observed, but no action will be done on events.
   void StopCheckingProgress();
 
+  // Loads the offline version of the URL in place of the current page.
+  void LoadOfflineReadingListEntry(web::NavigationItem* item);
+
+  // Returns if the current page with |url| has an offline version that can be
+  // displayed if the normal loading fails.
+  bool IsUrlAvailableOffline(const GURL& url) const;
+
+  // Checks if |item| should be observed or not.
+  // A non-null item should be observed if it is not already loading an offline
+  // URL.
+  bool ShouldObserveItem(web::NavigationItem* item) const;
+
   // WebContentsObserver implementation.
-  void DidStopLoading() override;
   void PageLoaded(
       web::PageLoadCompletionStatus load_completion_status) override;
   void WebStateDestroyed() override;
 
+  // Starts checking that the current navigation is loading quickly enough [1].
+  // If not, starts to load a distilled version of the page (if there is any).
+  // [1] A page loading quickly enough is a page that has loaded 25% within
+  // 1 second, 50% within 2 seconds and 75% within 3 seconds.
+  void DidStartLoading() override;
+
   ReadingListModel* reading_list_model_;
   std::unique_ptr<base::Timer> timer_;
   GURL pending_url_;