Change base::TickClock to a ref counted class.

components/copresence/timed_map.h

Index: components/copresence/timed_map.h
diff --git a/components/copresence/timed_map.h b/components/copresence/timed_map.h
index 7def76e4401b93c0c6786385daa634f9d64d9e8d..31fd153b917f92f12cbadc313d586c55918c1c87 100644
--- a/components/copresence/timed_map.h
+++ b/components/copresence/timed_map.h
@@ -52,8 +52,8 @@ class TimedMap {
     return elt == map_.end() ? kEmptyValue : elt->second;
   }
 
-  void set_clock_for_testing(scoped_ptr<base::TickClock> clock) {
-    clock_ = clock.Pass();
+  void set_clock_for_testing(const scoped_refptr<base::TickClock>& clock) {
+    clock_ = clock;
   }
 
  private:
@@ -83,7 +83,7 @@ class TimedMap {
 
   const ValueType kEmptyValue;
 
-  scoped_ptr<base::TickClock> clock_;
+  scoped_refptr<base::TickClock> clock_;
   base::RepeatingTimer<TimedMap> timer_;
   const base::TimeDelta lifetime_;
   const size_t max_elements_;