Change the RecentTabHelper to only capture the last one page in a 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 33 matching lines @@
 
   // Test support.
   // A factory that supplies the instances of an OfflinePageArchiver.
   // This is used for testing, where we want to use a specific mock.
   class TestArchiveFactory {
    public:
     virtual ~TestArchiveFactory() {}
     virtual std::unique_ptr<OfflinePageArchiver> CreateArchiver(
         content::WebContents* web_contents) = 0;
   };
-  // Test method, overrides the normally used MHTML Archivers with a test
-  // mocks created by specified function.
-  void SetArchiveFactoryForTest(
-      std::unique_ptr<TestArchiveFactory> test_archive_factory);
-  // Test method, overrides the task_runner_ so FastForwardBy() can be used.
-  void SetTaskRunnerForTest(
-      const scoped_refptr<base::SingleThreadTaskRunner>& task_runner);
+
+
+  // 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(
+        content::WebContents* web_contents) = 0;
+    virtual scoped_refptr<base::SingleThreadTaskRunner> GetTaskRunner() = 0;
+    // There is no expectations that tab_id is always present.
+    virtual bool GetTabId(content::WebContents* web_contents, int* tab_id) = 0;
+  };
+  void SetDelegate(std::unique_ptr<RecentTabHelper::Delegate> delegate);
 
  private:
   explicit RecentTabHelper(content::WebContents* web_contents);
   friend class content::WebContentsUserData<RecentTabHelper>;
 
 
+  void LazyInitialize();
   void ContinueSnapshotWithIdsToPurge(const std::vector<int64_t>& page_ids);
   void ContinueSnapshotAfterPurge(OfflinePageModel::DeletePageResult result);
   void SavePageCallback(OfflinePageModel::SavePageResult result,
                         int64_t offline_id);
 
   void ReportSnapshotCompleted();
   bool IsSamePage() const;
   ClientId client_id() const;
 
   // Page model is a service, no ownership.
   OfflinePageModel* page_model_;
-
   // If true, never make snapshots off the attached WebContents.
   bool never_do_snapshots_;
+  // If empty, the tab does not have AndroidId and can not capture pages.
+  std::string tab_id_;
 
   // The URL of the page that is currently being snapshotted. Used to check,
   // during async operations, that WebContents still contains the same page.
   GURL snapshot_url_;
   std::unique_ptr<SnapshotController> snapshot_controller_;
-  std::unique_ptr<TestArchiveFactory> test_archive_factory_;
+
+  std::unique_ptr<Delegate> delegate_;
 
   base::WeakPtrFactory<RecentTabHelper> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(RecentTabHelper);
 };
 
 }  // namespace offline_pages
 #endif  // CHROME_BROWSER_ANDROID_OFFLINE_PAGES_RECENT_TAB_HELPER_H_