Change base::TickClock to a ref counted class.

ui/events/test/event_generator.h

Index: ui/events/test/event_generator.h
diff --git a/ui/events/test/event_generator.h b/ui/events/test/event_generator.h
index bc243b9207145528fa6cffe560af9e3b3197ce6e..3240e35041468b596c3e37951864f4f8f304934f 100644
--- a/ui/events/test/event_generator.h
+++ b/ui/events/test/event_generator.h
@@ -10,6 +10,7 @@
 
 #include "base/basictypes.h"
 #include "base/callback.h"
+#include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/time/time.h"
 #include "ui/events/event_constants.h"
@@ -338,7 +339,7 @@ class EventGenerator {
   }
 
   // Specify an alternative tick clock to be used for simulating time in tests.
-  void SetTickClock(scoped_ptr<base::TickClock> tick_clock);
+  void SetTickClock(const scoped_refptr<base::TickClock>& tick_clock);
 
   // Get the current time from the tick clock.
   base::TimeDelta Now();
@@ -374,7 +375,7 @@ class EventGenerator {
   std::list<Event*> pending_events_;
   // Set to true to cause events to be posted asynchronously.
   bool async_;
-  scoped_ptr<base::TickClock> tick_clock_;
+  scoped_refptr<base::TickClock> tick_clock_;
 
   DISALLOW_COPY_AND_ASSIGN(EventGenerator);
 };