Load offline page if reading list entry takes more than 1s to load.

ios/chrome/browser/reading_list/reading_list_web_state_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 IOS_CHROME_BROWSER_READING_LIST_READING_LIST_WEB_STATE_OBSERVER_H_
+#define IOS_CHROME_BROWSER_READING_LIST_READING_LIST_WEB_STATE_OBSERVER_H_
+
+#include "base/macros.h"
+#include "base/timer/timer.h"
+#include "ios/web/public/web_state/web_state_observer.h"
+#include "ios/web/public/web_state/web_state_user_data.h"
+
+class BrowserState;
+class ReadingListModel;
+
+// Observes the loading of pages coming from the reading list and determines
+// whether and loading an offline version of the page is needed.
+class ReadingListWebStateObserver
+    : public web::WebStateUserData<ReadingListWebStateObserver>,
+      public web::WebStateObserver {
+ public:
+  static void CreateForWebState(web::WebState* web_state,
+                                web::BrowserState* browser_state);

[sdefresne, 2016/10/04 13:26:46]

You should pass a ios::ChromeBrowserState, only code in ios/web and BSKSF should
use web::BrowserState. Or better, since you only pass this to get the
ReadingListModel, just pass a ReadingListModel (this will make the code easier
to unit test).

+
+  ~ReadingListWebStateObserver() override;
+
+ private:
+  explicit ReadingListWebStateObserver(web::WebState* web_state,

[sdefresne, 2016/10/04 13:26:46]

"explicit" is for constructor with one parameter only (or with default values),
remove it from here.

+                                       web::BrowserState* browser_state);
+  friend class WebStateUserData<ReadingListWebStateObserver>;
+
+  // WebContentsObserver implementation.
+  void NavigationItemChanged() override;
+  void NavigationItemCommitted(
+      const web::LoadCommittedDetails& load_details) override;
+  void DidStartLoading() override;
+  void DidStopLoading() override;
+  void PageLoaded(
+      web::PageLoadCompletionStatus load_completion_status) override;
+  void WebStateDestroyed() override;
+
+ private:
+  // Heuristically determine if the reading list entry is loading quickly.
+  // If it doesn't load quickly, tries to load an offline version of the page.
+  void VerifyIfReadingListEntryStartedLoading();
+
+  web::WebState* web_state_;
+  ReadingListModel* reading_list_model_;
+  std::unique_ptr<base::Timer> timer_;
+
+  DISALLOW_COPY_AND_ASSIGN(ReadingListWebStateObserver);
+};
+
+#endif  // IOS_CHROME_BROWSER_READING_LIST_READING_LIST_WEB_STATE_OBSERVER_H_