[Dial] Refactor DialRegistry and DeviceDescriptionFetcher so they can be used by MediaSinkService

chrome/browser/extensions/api/dial/dial_registry.h

Index: chrome/browser/extensions/api/dial/dial_registry.h
diff --git a/chrome/browser/extensions/api/dial/dial_registry.h b/chrome/browser/extensions/api/dial/dial_registry.h
index e43d207bff830aa3fbecae52d6ea9a674cc9cc01..fb39d420d3808edd7ac51911037978af469c5e5f 100644
--- a/chrome/browser/extensions/api/dial/dial_registry.h
+++ b/chrome/browser/extensions/api/dial/dial_registry.h
@@ -70,6 +70,10 @@ class DialRegistry : public DialService::Observer,
   void OnListenerAdded();
   void OnListenerRemoved();
 
+  // This class does not take ownership of observer.
+  void RegisterObserver(Observer* observer);
+  void UnregisterObserver(Observer* observer);
+
   // Called by the DIAL API to try to kickoff a discovery if there is not one
   // already active.
   bool DiscoverNow();
@@ -111,6 +115,10 @@ class DialRegistry : public DialService::Observer,
   void OnNetworkChanged(
       net::NetworkChangeNotifier::ConnectionType type) override;
 
+  // Notify all observers about DialDeviceEvent or DialError.
+  void OnDialDeviceEvent(const DeviceList& devices);
+  void OnDialError(DialErrorCode type);
+
   // Starts and stops periodic discovery.  Periodic discovery is done when there
   // are registered event listeners.
   void StartPeriodicDiscovery();
@@ -178,7 +186,7 @@ class DialRegistry : public DialService::Observer,
 
   // Interface from which the DIAL API is notified of DIAL device events. the
   // DIAL API owns this DIAL registry.
-  Observer* const dial_api_;
+  std::set<Observer*> observers_;

[mark a. foltz, 2017/03/01 21:44:00]

Can you use base::ObserverList?

[zhaobin, 2017/03/02 07:04:35]

Done.

 
   FRIEND_TEST_ALL_PREFIXES(DialRegistryTest, TestAddRemoveListeners);
   FRIEND_TEST_ALL_PREFIXES(DialRegistryTest, TestNoDevicesDiscovered);