Fix cases where RunLoop is created without a MessageLoop.

chrome/browser/chromeos/login/screenshot_testing/screenshot_tester.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_LOGIN_SCREENSHOT_TESTING_SCREENSHOT_TESTER_H_
 #define CHROME_BROWSER_CHROMEOS_LOGIN_SCREENSHOT_TESTING_SCREENSHOT_TESTER_H_
 
 #include <string>
 #include <vector>
 
+#include "base/callback.h"
 #include "base/files/file_path.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted_memory.h"
 #include "base/memory/weak_ptr.h"
-#include "base/run_loop.h"
 #include "third_party/skia/include/core/SkBitmap.h"
 
 namespace chromeos {
 
 // A class that allows taking, saving and comparing screnshots while
 // running tests.
 class ScreenshotTester {
  public:
   ScreenshotTester();
   virtual ~ScreenshotTester();
@@ skipping 104 matching lines @@
   Result CompareScreenshotsRegularly(SkBitmap model_bitmap,
                                      SkBitmap sample_bitmap);
 
   // Path to the directory for golden screenshots.
   base::FilePath golden_screenshots_dir_;
 
   // Path to the directory where screenshots that failed comparing
   // and difference between them and golden ones will be stored.
   base::FilePath artifacts_dir_;
 
-  // |run_loop_| and |run_loop_quitter_| are used to synchronize
-  // with ui::GrabWindowSnapshotAsync.
-  base::RunLoop run_loop_;
+  // |run_loop_quitter_| is used to stop waiting when
+  // ui::GrabWindowSnapshotAsync completes.
   base::Closure run_loop_quitter_;
 
   // Is true when we're in test mode:
   // comparing golden screenshots and current ones.
   bool test_mode_;
 
   // Is true when switches specify that PerceptualDiff should
   // be used to compare images.
   bool pdiff_enabled_;
 
   // Is true when switches specify that artifacts should be saved somewhere.
   bool generate_artifacts_;
 
   // Vector which holds areas which the comparison ignores because
   // them being different is not a bug (e.g. time on the clock).
   std::vector<SkIRect> ignored_areas_;
 
   base::WeakPtrFactory<ScreenshotTester> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ScreenshotTester);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_LOGIN_SCREENSHOT_TESTING_SCREENSHOT_TESTER_H_