[MediaRouter] Record DIAL device counts in DialMediaSinkServiceImpl

chrome/browser/media/router/media_router_metrics.cc

Index: chrome/browser/media/router/media_router_metrics.cc
diff --git a/chrome/browser/media/router/media_router_metrics.cc b/chrome/browser/media/router/media_router_metrics.cc
index 3da4c634908d4ac17a1f8b82f1630b71f3d38a79..a64b98a813f488d074580d490e4188ca4ef9b2eb 100644
--- a/chrome/browser/media/router/media_router_metrics.cc
+++ b/chrome/browser/media/router/media_router_metrics.cc
@@ -6,10 +6,23 @@
 
 #include "base/macros.h"
 #include "base/metrics/histogram_macros.h"
+#include "base/time/default_clock.h"
+
+namespace {
+// How long to wait between device counts metrics are recorded. Set to 1 hour.
+const int kDeviceCountMetricThresholdMins = 60;

[Ilya Sherman, 2017/06/07 04:57:03]

What's the reason for this?  What's the motivation for recording the metric
repeatedly, roughly once per hour?

[zhaobin, 2017/06/07 20:45:56]

To keep device count recording mechanism in browser the same as that in
extensions
(https://cs.corp.google.com/piper///depot/google3/chrome_platform/media_router...)

We are moving device discovery from extension (old code) to browser (new code).
We want to compare device count found by new code and old code, and need to keep
recording mechanism the same.

+}  // namespace
 
 namespace media_router {
 
+MediaRouterMetrics::MediaRouterMetrics() : clock_(new base::DefaultClock()) {}
+MediaRouterMetrics::~MediaRouterMetrics() = default;
+
 // static
+const char MediaRouterMetrics::kHistogramDialAvailableDeviceCount[] =
+    "MediaRouter.Dial.AvailableDevicesCount";
+const char MediaRouterMetrics::kHistogramDialKnownDeviceCount[] =
+    "MediaRouter.Dial.KnownDevicesCount";
 const char MediaRouterMetrics::kHistogramIconClickLocation[] =
     "MediaRouter.Icon.Click.Location";
 const char MediaRouterMetrics::kHistogramUiDialogPaint[] =
@@ -63,4 +76,20 @@ void MediaRouterMetrics::RecordRouteCreationOutcome(
       static_cast<int>(MediaRouterRouteCreationOutcome::TOTAL_COUNT));
 }
 
+void MediaRouterMetrics::RecordDialDeviceCounts(size_t available_device_count,
+                                                size_t known_device_count) {
+  if (clock_->Now() - device_count_metrics_record_time_ <
+      base::TimeDelta::FromMinutes(kDeviceCountMetricThresholdMins)) {
+    return;
+  }
+  UMA_HISTOGRAM_COUNTS_100(kHistogramDialAvailableDeviceCount,
+                           available_device_count);
+  UMA_HISTOGRAM_COUNTS_100(kHistogramDialKnownDeviceCount, known_device_count);
+  device_count_metrics_record_time_ = clock_->Now();
+}
+
+void MediaRouterMetrics::SetClockForTest(std::unique_ptr<base::Clock> clock) {
+  clock_ = std::move(clock);
+}
+
 }  // namespace media_router