Add browser test for CustomizationWallpaperDownloader.

chrome/browser/chromeos/customization_wallpaper_downloader.h

 // Copyright 2014 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_CHROMEOS_CUSTOMIZATION_WALLPAPER_DOWNLOADER_H_
 #define CHROME_BROWSER_CHROMEOS_CUSTOMIZATION_WALLPAPER_DOWNLOADER_H_
 
 #include <string>
 
 #include "base/bind.h"
@@ skipping 34 matching lines @@
           on_wallpaper_fetch_completed);
 
   virtual ~CustomizationWallpaperDownloader();
 
   // Start download.
   void Start();
 
   // net::URLFetcherDelegate
   virtual void OnURLFetchComplete(const net::URLFetcher* source) OVERRIDE;
 
+  // This is called in tests to modify (lower) retry delay.
+  void set_retry_delay_for_testing(base::TimeDelta value) {
+    retry_delay_ = value;
+  }
+
  private:
   // Start new request.
   void StartRequest();
 
   // Schedules retry.
   void Retry();
 
   // Called on UI thread.
   void OnWallpaperDirectoryCreated(scoped_ptr<bool> success);
 
@@ skipping 17 matching lines @@
 
   // Full path to temporary file to fetch downloaded wallpper.
   const base::FilePath wallpaper_temporary_file_;
 
   // Pending retry.
   base::OneShotTimer<CustomizationWallpaperDownloader> request_scheduled_;
 
   // Number of download retries (first attempt is not counted as retry).
   size_t retries_;
 
+  // Sleep between retry requests (increasing, see Retry() method for details).
+  // Non-constant value for tests.
+  base::TimeDelta retry_delay_;
+
   // Callback supplied by caller.
   base::Callback<void(bool success, const GURL&)> on_wallpaper_fetch_completed_;
 
   base::WeakPtrFactory<CustomizationWallpaperDownloader> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(CustomizationWallpaperDownloader);
 };
 
 }  //   namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_CUSTOMIZATION_WALLPAPER_DOWNLOADER_H_