Fix implicit scoped_refptr<T> to T* conversion in TestMetroViewerProcessHost

ash/test/test_metro_viewer_process_host.h

 // Copyright (c) 2013 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 ASH_TEST_TEST_METRO_VIEWER_PROCESS_HOST_H_
 #define ASH_TEST_TEST_METRO_VIEWER_PROCESS_HOST_H_
 
 #include "base/memory/scoped_ptr.h"
 #include "win8/viewer/metro_viewer_process_host.h"
 
 class AcceleratedSurface;
 
 namespace ash {
 namespace test {
 
 class TestMetroViewerProcessHost : public win8::MetroViewerProcessHost {
  public:
-  TestMetroViewerProcessHost(base::SingleThreadTaskRunner* ipc_task_runner);
+  TestMetroViewerProcessHost(
+      const scoped_refptr<base::SingleThreadTaskRunner>& ipc_task_runner);
   virtual ~TestMetroViewerProcessHost();
 
   bool closed_unexpectedly() { return closed_unexpectedly_; }
 
   // Forcibly terminate the viewer. Used on completion of tests to ensure that
   // it's gone (quickly) so that we can start the next test immediately.
   void TerminateViewer();
 
  private:
   // win8::MetroViewerProcessHost implementation
   virtual void OnChannelError() override;
   virtual void OnSetTargetSurface(gfx::NativeViewId target_surface,
                                   float device_scale) override;
   virtual void OnOpenURL(const base::string16& url) override;
   virtual void OnHandleSearchRequest(
       const base::string16& search_string) override;
   virtual void OnWindowSizeChanged(uint32 width, uint32 height) override;
 
   bool closed_unexpectedly_;
 
   DISALLOW_COPY_AND_ASSIGN(TestMetroViewerProcessHost);
 };
 
 
 }  // namespace test
 }  // namespace ash
 
 #endif  // ASH_TEST_TEST_METRO_VIEWER_PROCESS_HOST_H_