[Device Discovery] Make DialRegistry a Singleton

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 12250ff40a657b40705dbfbf4a0aaa3614210aac..e7e4eb685d83d0093c94661a0110bc93950643a6 100644
--- a/chrome/browser/media/router/discovery/dial/dial_registry.h
+++ b/chrome/browser/media/router/discovery/dial/dial_registry.h
@@ -21,6 +21,7 @@
 #include "base/timer/timer.h"
 #include "chrome/browser/media/router/discovery/dial/dial_service.h"
 #include "chrome/browser/profiles/profile.h"
+#include "components/keyed_service/core/refcounted_keyed_service.h"
 #include "net/base/network_change_notifier.h"
 
 namespace media_router {
@@ -29,7 +30,8 @@ namespace media_router {
 // the observer with an updated, complete set of active devices.  The registry's
 // observer (i.e., the Dial API) owns the registry instance.
 // DialRegistry lives on the IO thread.
-class DialRegistry : public DialService::Observer,
+class DialRegistry : public RefcountedKeyedService,

[mark a. foltz, 2017/03/18 18:04:58]

I don't think the DialRegistry needs to be a keyed service - it should have the
same set of devices across profiles, so only one needs to be created per browser
process.   Maybe just make it base::RefCounted<>?

[zhaobin, 2017/03/22 02:48:45]

Code removed.

+                     public DialService::Observer,
                      public net::NetworkChangeNotifier::NetworkChangeObserver {
  public:
   using DeviceList = std::vector<DialDeviceData>;
@@ -60,8 +62,6 @@ class DialRegistry : public DialService::Observer,
                base::TimeDelta expiration,
                const size_t max_devices);
 
-  ~DialRegistry() override;
-
   // 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.
@@ -86,6 +86,8 @@ class DialRegistry : public DialService::Observer,
   void AddDeviceForTest(const DialDeviceData& device_data);
 
  protected:
+  ~DialRegistry() override;
+
   // Returns a new instance of the DIAL service.  Overridden by tests.
   virtual std::unique_ptr<DialService> CreateDialService();
   virtual void ClearDialService();
@@ -101,6 +103,9 @@ class DialRegistry : public DialService::Observer,
       base::hash_map<std::string, std::unique_ptr<DialDeviceData>>;
   using DeviceByLabelMap = std::map<std::string, DialDeviceData*>;
 
+  // RefcountedKeyedService:
+  void ShutdownOnUIThread() override;
+
   // DialService::Observer:
   void OnDiscoveryRequest(DialService* service) override;
   void OnDeviceDiscovered(DialService* service,