Last_n: Do not save a snapshot of a closing tab.

chrome/browser/android/offline_pages/recent_tab_helper.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_ANDROID_OFFLINE_PAGES_RECENT_TAB_HELPER_H_
 #define CHROME_BROWSER_ANDROID_OFFLINE_PAGES_RECENT_TAB_HELPER_H_
 
 #include <memory>
 #include <vector>
 
@@ skipping 22 matching lines @@
  public:
   ~RecentTabHelper() override;
 
   // content::WebContentsObserver
   void DidFinishNavigation(
       content::NavigationHandle* navigation_handle) override;
   void DocumentAvailableInMainFrame() override;
   void DocumentOnLoadCompletedInMainFrame() override;
   void WebContentsDestroyed() override;
   void WasHidden() override;
+  void WasShown() override;
+
+  // Notifies that the tab of the associated WebContents will (most probably) be
+  // closed. This call is expected to always happen before the one to WasHidden.
+  void WillCloseTab();
 
   // SnapshotController::Client
   void StartSnapshot() override;
 
   // Delegate that is used by RecentTabHelper to get external dependencies.
   // Default implementation lives in .cc file, while tests provide an override.
   class Delegate {
    public:
     virtual ~Delegate() {}
     virtual std::unique_ptr<OfflinePageArchiver> CreatePageArchiver(
@@ skipping 84 matching lines @@
   // is also used as an initialization flag for EnsureInitialized() to be run
   // only once.
   std::unique_ptr<SnapshotController> snapshot_controller_;
 
   std::unique_ptr<Delegate> delegate_;
 
   // Set at each navigation to control if last_n should save snapshots of the
   // current page being loaded.
   bool last_n_listen_to_tab_hidden_ = false;
 
+  // Set to true when the tab containing the associated WebContents is in the
+  // process of being closed.
+  bool tab_is_closing = false;

[Dmitry Titov, 2017/02/24 01:49:38]

Nit: add "_" at the end of the name.

[carlosk, 2017/02/24 02:06:35]

Done.

+
   base::WeakPtrFactory<RecentTabHelper> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(RecentTabHelper);
 };
 
 }  // namespace offline_pages
 
 #endif  // CHROME_BROWSER_ANDROID_OFFLINE_PAGES_RECENT_TAB_HELPER_H_