[MediaRouter] Record DIAL device counts in DialMediaSinkServiceImpl

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

 // 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.
 
 #include "chrome/browser/media/router/discovery/dial/dial_media_sink_service_impl.h"
 
 #include "chrome/browser/media/router/discovery/dial/dial_device_data.h"
+#include "chrome/browser/media/router/media_router_metrics.h"
 #include "chrome/browser/profiles/profile.h"
 #include "content/public/browser/browser_thread.h"
 #include "net/url_request/url_request_context_getter.h"
 
 using content::BrowserThread;
 
+namespace {
+// How long to wait between device counts metrics are recorded. Set to 1 hour.
+const int kDeviceCountMetricThresholdMins = 60 * 60;

[imcheng, 2017/06/02 21:34:51]

I think this should be just 60?

[zhaobin, 2017/06/05 23:20:55]

Fixed in media_router_metrics.cc

+}
+
 namespace media_router {
 
 DialMediaSinkServiceImpl::DialMediaSinkServiceImpl(
     const OnSinksDiscoveredCallback& callback,
     net::URLRequestContextGetter* request_context)
     : MediaSinkServiceBase(callback), request_context_(request_context) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
   DCHECK(request_context_);
 }
 
@@ skipping 98 matching lines @@
   MediaSinkServiceBase::RestartTimer();
 }
 
 void DialMediaSinkServiceImpl::OnDeviceDescriptionError(
     const DialDeviceData& device,
     const std::string& error_message) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
   DVLOG(2) << "OnDescriptionFetchesError [message]: " << error_message;
 }
 
+void DialMediaSinkServiceImpl::RecordDeviceCounts() {
+  if (base::Time::Now() - device_count_metrics_record_time_ <

[imcheng, 2017/06/02 21:34:51]

Can the time check logic be part of MediaSinkServiceBase? That way, it can be
shared with other implementations.

[mark a. foltz, 2017/06/02 22:06:40]

I would rather bookkeeping for recording UMA live in MediaRouterMetrics, unless
there is some state that is tied to a specific instance of an object.  I think
DMSS is a singleton so maybe we can move this.

[zhaobin, 2017/06/05 23:20:55]

Done.

+      base::TimeDelta::FromMinutes(kDeviceCountMetricThresholdMins)) {
+    return;
+  }
+  MediaRouterMetrics::RecordDialDeviceCounts(current_sinks_.size(),
+                                             current_devices_.size());
+  device_count_metrics_record_time_ = base::Time::Now();
+}
+
 }  // namespace media_router