Change base::TickClock to a ref counted class.

chrome/browser/media/cast_transport_host_filter.h

Index: chrome/browser/media/cast_transport_host_filter.h
diff --git a/chrome/browser/media/cast_transport_host_filter.h b/chrome/browser/media/cast_transport_host_filter.h
index 3a419cc5c8106471b8810ac7c0506d8364a326b1..da3175a82781a7ad3a18abe66019bb2faa573a24 100644
--- a/chrome/browser/media/cast_transport_host_filter.h
+++ b/chrome/browser/media/cast_transport_host_filter.h
@@ -8,13 +8,16 @@
 #include "base/id_map.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
-#include "base/time/default_tick_clock.h"
 #include "chrome/common/cast_messages.h"
 #include "content/public/browser/browser_message_filter.h"
 #include "media/cast/cast_sender.h"
 #include "media/cast/logging/logging_defines.h"
 #include "media/cast/net/cast_transport_sender.h"
 
+namespace base {
+class DefaultTickClock;
+}
+
 namespace content {
 class PowerSaveBlocker;
 }  // namespace content
@@ -71,7 +74,7 @@ class CastTransportHostFilter : public content::BrowserMessageFilter {
   IDMap<media::cast::CastTransportSender, IDMapOwnPointer> id_map_;
 
   // Clock used by Cast transport.
-  base::DefaultTickClock clock_;
+  scoped_refptr<base::DefaultTickClock> clock_;
 
   // While |id_map_| is non-empty, hold an instance of
   // content::PowerSaveBlocker.  This prevents Chrome from being suspended while