Change base::TickClock to a ref counted class.

ui/display/chromeos/x11/native_display_event_dispatcher_x11.h

Index: ui/display/chromeos/x11/native_display_event_dispatcher_x11.h
diff --git a/ui/display/chromeos/x11/native_display_event_dispatcher_x11.h b/ui/display/chromeos/x11/native_display_event_dispatcher_x11.h
index e3ff9c00fff831a13b16ff0207acd5bfd51cfc41..aaac4c69e7a24f161b852c0575d358661665e1c5 100644
--- a/ui/display/chromeos/x11/native_display_event_dispatcher_x11.h
+++ b/ui/display/chromeos/x11/native_display_event_dispatcher_x11.h
@@ -28,7 +28,7 @@ class DISPLAY_EXPORT NativeDisplayEventDispatcherX11
   virtual bool CanDispatchEvent(const PlatformEvent& event) override;
   virtual uint32_t DispatchEvent(const PlatformEvent& event) override;
 
-  void SetTickClockForTest(scoped_ptr<base::TickClock> tick_clock);
+  void SetTickClockForTest(scoped_refptr<base::TickClock> tick_clock);
 
   // How long the cached output is valid after startup.
   static const int kUseCacheAfterStartupMs;
@@ -42,7 +42,7 @@ class DISPLAY_EXPORT NativeDisplayEventDispatcherX11
 
   base::TimeTicks startup_time_;
 
-  scoped_ptr<base::TickClock> tick_clock_;
+  scoped_refptr<base::TickClock> tick_clock_;
 
   DISALLOW_COPY_AND_ASSIGN(NativeDisplayEventDispatcherX11);
 };