[MediaRouter] Record DIAL device counts in DialMediaSinkServiceImpl

chrome/browser/media/router/media_router_metrics.h

 // Copyright 2015 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_MEDIA_ROUTER_METRICS_H_
 #define CHROME_BROWSER_MEDIA_ROUTER_MEDIA_ROUTER_METRICS_H_
 
+#include <memory>
+
 #include "base/gtest_prod_util.h"
+#include "base/time/clock.h"
 #include "base/time/time.h"
 
 namespace media_router {
 
 // NOTE: Do not renumber enums as that would confuse interpretation of
 // previously logged data. When making changes, also update the enum list
 // in tools/metrics/histograms/histograms.xml to keep it in sync.
 
 // NOTE: For metrics specific to the Media Router component extension, see
 // mojo/media_router_mojo_metrics.h.
@@ skipping 28 matching lines @@
   CLOSE = 3,
   STATUS_REMOTE = 4,
   REPLACE_LOCAL_ROUTE = 5,
 
   // Note: Add entries only immediately above this line.
   TOTAL_COUNT = 6
 };
 
 class MediaRouterMetrics {
  public:
+  MediaRouterMetrics();
+  ~MediaRouterMetrics();
+
   // UMA histogram names.
+  static const char kDialAvailableDeviceCount[];

[mark a. foltz, 2017/06/06 23:45:00]

kHistogramDialAvailableDeviceCount (and similarly below)

[zhaobin, 2017/06/07 02:05:59]

Done.

+  static const char kDialKnownDeviceCount[];
   static const char kHistogramIconClickLocation[];
   static const char kHistogramUiDialogPaint[];
   static const char kHistogramUiDialogLoadedWithData[];
   static const char kHistogramUiFirstAction[];
   static const char kHistogramRouteCreationOutcome[];
 
   // Records where the user clicked to open the Media Router dialog.
   static void RecordMediaRouterDialogOrigin(
       MediaRouterDialogOpenOrigin origin);
 
   // Records the duration it takes for the Media Router dialog to open and
   // finish painting after a user clicks to open the dialog.
   static void RecordMediaRouterDialogPaint(
       const base::TimeDelta delta);
 
   // Records the duration it takes for the Media Router dialog to load its
   // initial data after a user clicks to open the dialog.
   static void RecordMediaRouterDialogLoaded(
       const base::TimeDelta delta);
 
   // Records the first action the user took after the Media Router dialog
   // opened.
   static void RecordMediaRouterInitialUserAction(
       MediaRouterUserAction action);
 
   // Records the outcome in a create route response.
   static void RecordRouteCreationOutcome(
       MediaRouterRouteCreationOutcome outcome);
+
+  // Records device counts.
+  void RecordDialDeviceCounts(size_t available_device_count,
+                              size_t known_device_count);
+
+  // Allows tests to swap in a fake clock.
+  void SetClockForTest(std::unique_ptr<base::Clock> clock);
+
+ private:
+  base::Time device_count_metrics_record_time_;
+
+  std::unique_ptr<base::Clock> clock_;
 };
 
 }  // namespace media_router
 
 #endif  // CHROME_BROWSER_MEDIA_ROUTER_MEDIA_ROUTER_METRICS_H_