[DIAL tests] Slightly improve DialRegistry tests.

chrome/browser/media/router/discovery/dial/dial_registry.h

Index: chrome/browser/media/router/discovery/dial/dial_registry.h
diff --git a/chrome/browser/media/router/discovery/dial/dial_registry.h b/chrome/browser/media/router/discovery/dial/dial_registry.h
index 962533727f4aa2ac641f5e6d53c7594fd342b048..55281e0e06ccf3fb71b586d6386e4883852548e5 100644
--- a/chrome/browser/media/router/discovery/dial/dial_registry.h
+++ b/chrome/browser/media/router/discovery/dial/dial_registry.h
@@ -17,12 +17,15 @@
 #include "base/macros.h"
 #include "base/memory/singleton.h"
 #include "base/observer_list.h"
-#include "base/time/time.h"
 #include "base/timer/timer.h"
 #include "chrome/browser/media/router/discovery/dial/dial_service.h"
 #include "chrome/browser/profiles/profile.h"
 #include "net/base/network_change_notifier.h"
 
+namespace base {
+class Clock;
+}
+
 namespace media_router {
 
 // Keeps track of devices that have responded to discovery requests and notifies
@@ -85,14 +88,14 @@ class DialRegistry : public DialService::Observer,
   // removed by PruneExpiredDevices().
   void AddDeviceForTest(const DialDeviceData& device_data);
 
+  // Allows tests to swap in a fake clock.
+  void SetClockForTest(std::unique_ptr<base::Clock> clock);
+
  protected:
   // Returns a new instance of the DIAL service.  Overridden by tests.
   virtual std::unique_ptr<DialService> CreateDialService();
   virtual void ClearDialService();
 
-  // Returns the current time.  Overridden by tests.
-  virtual base::Time Now() const;
-
   // The DIAL service. Periodic discovery is active when this is not NULL.
   std::unique_ptr<DialService> dial_;
 
@@ -189,6 +192,8 @@ class DialRegistry : public DialService::Observer,
   // DIAL API owns this DIAL registry.
   base::ObserverList<Observer> observers_;
 
+  std::unique_ptr<base::Clock> clock_;
+
   FRIEND_TEST_ALL_PREFIXES(DialRegistryTest, TestAddRemoveListeners);
   FRIEND_TEST_ALL_PREFIXES(DialRegistryTest, TestNoDevicesDiscovered);
   FRIEND_TEST_ALL_PREFIXES(DialRegistryTest, TestDevicesDiscovered);