[Device Discovery] Make DialRegistry a Singleton

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

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_MEDIA_ROUTER_DISCOVERY_DIAL_DIAL_REGISTRY_H_
 #define CHROME_BROWSER_MEDIA_ROUTER_DISCOVERY_DIAL_DIAL_REGISTRY_H_
 
 #include <stddef.h>
 
 #include <map>
 #include <memory>
 #include <string>
 #include <vector>
 
 #include "base/containers/hash_tables.h"
 #include "base/gtest_prod_util.h"
 #include "base/macros.h"
-#include "base/memory/ref_counted.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 media_router {
 
 // Keeps track of devices that have responded to discovery requests and notifies
@@ skipping 18 matching lines @@
    public:
     // Methods invoked on the IO thread when a new device is discovered, an
     // update is triggered by dial.discoverNow or an error occured.
     virtual void OnDialDeviceEvent(const DeviceList& devices) = 0;
     virtual void OnDialError(DialErrorCode type) = 0;
 
    protected:
     virtual ~Observer() {}
   };
 
-  // Create the DIAL registry and pass a reference to allow it to notify on
-  // DIAL device events.
-  DialRegistry(base::TimeDelta refresh_interval,
-               base::TimeDelta expiration,
-               const size_t max_devices);
-
-  ~DialRegistry() override;
+  static DialRegistry* GetInstance();
 
   // Called by the DIAL API when event listeners are added or removed. The dial
   // service is started after the first listener is added and stopped after the
   // last listener is removed.
   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();
 
+  // Starts and stops periodic discovery.  Periodic discovery is done when there
+  // are registered event listeners.
+  void StartPeriodicDiscovery();
+  void StopPeriodicDiscovery();
+
   // Returns the URL of the device description for the device identified by
   // |label|, or an empty GURL if no such device exists.
   GURL GetDeviceDescriptionURL(const std::string& label) const;
 
   // Adds a device directly to the registry as if it was discovered.  For tests
   // only.  Note that if discovery is actually started, this device will be
   // removed by PruneExpiredDevices().
   void AddDeviceForTest(const DialDeviceData& device_data);
 
  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_;
 
  private:
   using DeviceByIdMap =
       base::hash_map<std::string, std::unique_ptr<DialDeviceData>>;
   using DeviceByLabelMap = std::map<std::string, DialDeviceData*>;
 
+  friend class MockDialRegistry;
+  friend struct base::DefaultSingletonTraits<DialRegistry>;
+
+  // Create the DIAL registry and pass a reference to allow it to notify on

[imcheng, 2017/03/23 23:06:00]

nit: Remove this comment as it's not very useful. Move the second part of
sentence to RegisterObserver with some rewording.

[zhaobin, 2017/03/24 00:42:35]

Done.

+  // DIAL device events.
+  DialRegistry();
+  ~DialRegistry() override;
+
   // DialService::Observer:
   void OnDiscoveryRequest(DialService* service) override;
   void OnDeviceDiscovered(DialService* service,
                           const DialDeviceData& device) override;
   void OnDiscoveryFinished(DialService* service) override;
   void OnError(DialService* service,
                const DialService::DialServiceErrorCode& code) override;
 
   // net::NetworkChangeObserver:
   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();
-  void StopPeriodicDiscovery();
 
   // Check whether we are in a state ready to discover and dispatch error
   // notifications if not.
   bool ReadyToDiscover();
 
   // Purge our whole registry. We may need to do this occasionally, e.g. when
   // the network status changes.  Increments the registry generation.
   void Clear();
 
   // The repeating timer schedules discoveries with this method.
@@ skipping 38 matching lines @@
   const base::TimeDelta expiration_delta_;
   const size_t max_devices_;
 
   // A map used to track known devices by their device_id.
   DeviceByIdMap device_by_id_map_;
 
   // A map used to track known devices sorted by label.  We iterate over this to
   // construct the device list sent to API clients.
   DeviceByLabelMap device_by_label_map_;
 
-  // Timer used to manage periodic discovery requests.
-  base::RepeatingTimer repeating_timer_;
+  // Timer used to manage periodic discovery requests. Timer is created and
+  // destroyed on IO thread.
+  std::unique_ptr<base::RepeatingTimer> repeating_timer_;
 
   // Interface from which the DIAL API is notified of DIAL device events. the
   // DIAL API owns this DIAL registry.
   base::ObserverList<Observer> observers_;
 
   FRIEND_TEST_ALL_PREFIXES(DialRegistryTest, TestAddRemoveListeners);
   FRIEND_TEST_ALL_PREFIXES(DialRegistryTest, TestNoDevicesDiscovered);
   FRIEND_TEST_ALL_PREFIXES(DialRegistryTest, TestDevicesDiscovered);
   FRIEND_TEST_ALL_PREFIXES(DialRegistryTest,
                            TestDevicesDiscoveredWithTwoListeners);
   FRIEND_TEST_ALL_PREFIXES(DialRegistryTest, TestDeviceExpires);
   FRIEND_TEST_ALL_PREFIXES(DialRegistryTest, TestExpiredDeviceIsRediscovered);
   FRIEND_TEST_ALL_PREFIXES(DialRegistryTest,
                            TestRemovingListenerDoesNotClearList);
   FRIEND_TEST_ALL_PREFIXES(DialRegistryTest, TestNetworkEventConnectionLost);
   FRIEND_TEST_ALL_PREFIXES(DialRegistryTest,
                            TestNetworkEventConnectionRestored);
   DISALLOW_COPY_AND_ASSIGN(DialRegistry);
 };
 
 }  // namespace media_router
 
 #endif  // CHROME_BROWSER_MEDIA_ROUTER_DISCOVERY_DIAL_DIAL_REGISTRY_H_