Introduce ThreadTaskRunnerHandle::OverrideForTesting and TestMockTimeTaskRunner::ScopedContext.

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 @@
   // 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(
         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;
     virtual bool IsLowEndDevice() = 0;
   };
   void SetDelegate(std::unique_ptr<RecentTabHelper::Delegate> delegate);
 
   // Creates a request to download the current page with a properly filled
   // |client_id| and valid |request_id| issued by RequestCoordinator from a
   // suspended request. This method might be called multiple times for the same
   // page at any point after its navigation commits. There are some important
@@ skipping 80 matching lines @@
   bool last_n_listen_to_tab_hidden_ = false;
 
   base::WeakPtrFactory<RecentTabHelper> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(RecentTabHelper);
 };
 
 }  // namespace offline_pages
 
 #endif  // CHROME_BROWSER_ANDROID_OFFLINE_PAGES_RECENT_TAB_HELPER_H_