Change the RecentTabHelper to only capture the last one page in a tab.

chrome/browser/android/offline_pages/recent_tab_helper.h

Index: chrome/browser/android/offline_pages/recent_tab_helper.h
diff --git a/chrome/browser/android/offline_pages/recent_tab_helper.h b/chrome/browser/android/offline_pages/recent_tab_helper.h
index 025f52b8fbce9d61a67d79cb7270e2b931dd1321..8d65fa9e9ab4c2539aa1a78ff3e07a6defe7f0c6 100644
--- a/chrome/browser/android/offline_pages/recent_tab_helper.h
+++ b/chrome/browser/android/offline_pages/recent_tab_helper.h
@@ -51,19 +51,27 @@ class RecentTabHelper
     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,
@@ -75,15 +83,17 @@ class RecentTabHelper
 
   // 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_;