[MediaRouter] Record DIAL device counts in DialMediaSinkServiceImpl

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

 // Copyright 2017 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_MEDIA_SINK_SERVICE_IMPL_H_
 #define CHROME_BROWSER_MEDIA_ROUTER_DISCOVERY_DIAL_DIAL_MEDIA_SINK_SERVICE_IMPL_H_
 
 #include <memory>
 #include <set>
 
@@ skipping 45 matching lines @@
   // Called when description service successfully fetches and parses device
   // description XML. Restart |finish_timer_| if it is not running.
   void OnDeviceDescriptionAvailable(
       const DialDeviceData& device_data,
       const ParsedDialDeviceDescription& description_data);
 
   // Called when fails to fetch or parse device description XML.
   void OnDeviceDescriptionError(const DialDeviceData& device,
                                 const std::string& error_message);
 
+  // MediaSinkServiceBase implementation.
+  void RecordDeviceCounts() override;
+
   std::unique_ptr<DeviceDescriptionService> description_service_;
 
   // Raw pointer to DialRegistry singleton.
   DialRegistry* dial_registry_ = nullptr;
 
   // DialRegistry for unit test.
   DialRegistry* test_dial_registry_ = nullptr;
 
   // Device data list from current round of discovery.
   DialRegistry::DeviceList current_devices_;
 
   scoped_refptr<net::URLRequestContextGetter> request_context_;
+
+  base::Time device_count_metrics_record_time_;
 };
 
 }  // namespace media_router
 
 #endif  // CHROME_BROWSER_MEDIA_ROUTER_DISCOVERY_DIAL_DIAL_MEDIA_SINK_SERVICE_IMPL_H_