Add P2 UMA metrics for Media Router device click latency.

This change adds the following metric:
- The time it takes for the user to select a device after viewing a populated device list.

BUG=547977

Review URL: https://codereview.chromium.org/1555353002

Cr-Commit-Position: refs/heads/master@{#368775}

6 files changed, 94 insertions, 0 deletions

diff --git a/chrome/browser/resources/media_router/elements/media_router_container/media_router_container.js b/chrome/browser/resources/media_router/elements/media_router_container/media_router_container.js
index 66ee578..c69d71e 100644
--- a/chrome/browser/resources/media_router/elements/media_router_container/media_router_container.js
+++ b/chrome/browser/resources/media_router/elements/media_router_container/media_router_container.js
@@ -162,6 +162,17 @@ Polymer({
     },
 
     /**
+     * The time the sink list was shown and populated with at least one sink.
+     * This is reset whenever the user switches views or there are no sinks
+     * available for display.
+     * @private {number}
+     */
+    populatedSinkListSeenTimeMs_: {
+      type: Number,
+      value: -1,
+    },
+
+    /**
      * The list of current routes.
      * @type {!Array<!media_router.Route>}
      */
@@ -271,6 +282,10 @@ Polymer({
     'mouseenter': 'onMouseEnter_',
   },
 
+  observers: [
+    'maybeUpdateStartSinkDisplayStartTime_(currentView_, sinksToShow_)',
+  ],
+
   ready: function() {
     this.showSinkList_();
   },
@@ -658,6 +673,29 @@ Polymer({
   },
 
   /**
+   * May update |populatedSinkListSeenTimeMs_| depending on |currentView| and
+   * |sinksToShow|.
+   * Called when |currentView_| or |sinksToShow_| is updated.
+   *
+   * @param {?media_router.MediaRouterView} currentView The current view of the
+   *                                        dialog.
+   * @param {!Array<!media_router.Sink>} sinksToShow The sinks to display.
+   * @private
+   */
+  maybeUpdateStartSinkDisplayStartTime_: function(currentView, sinksToShow) {
+    if (currentView == media_router.MediaRouterView.SINK_LIST &&
+        sinksToShow.length != 0) {
+      // Only set |populatedSinkListSeenTimeMs_| if it has not already been set.
+      if (this.populatedSinkListSeenTimeMs_ == -1)
+        this.populatedSinkListSeenTimeMs_ = performance.now();
+    } else {
+      // Reset |populatedSinkListLastSeen_| if the sink list isn't being shown
+      // or if there aren't any sinks available for display.
+      this.populatedSinkListSeenTimeMs_ = -1;
+    }
+  },
+
+  /**
    * Handles a cast mode selection. Updates |headerText|, |headerTextTooltip|,
    * and |shownCastModeValue_|.
    *
@@ -892,6 +930,10 @@ Polymer({
                 sink.castModes & -sink.castModes : this.shownCastModeValue_
       });
       this.currentLaunchingSinkId_ = sink.id;
+
+      var timeToSelectSink =
+          performance.now() - this.populatedSinkListSeenTimeMs_;
+      this.fire('report-sink-click-time', {timeMs: timeToSelectSink});
     }
   },
 
diff --git a/chrome/browser/resources/media_router/media_router.js b/chrome/browser/resources/media_router/media_router.js
index 9d7ca18..2f497b9 100644
--- a/chrome/browser/resources/media_router/media_router.js
+++ b/chrome/browser/resources/media_router/media_router.js
@@ -36,6 +36,8 @@ cr.define('media_router', function() {
                                onNavigateToDetails);
     container.addEventListener('navigate-to-cast-mode-list',
                                onNavigateToCastMode);
+    container.addEventListener('report-sink-click-time',
+                               onSinkClickTimeReported);
     container.addEventListener('report-sink-count', onSinkCountReported);
     container.addEventListener('show-initial-state', onShowInitialState);
     container.addEventListener('sink-click', onSinkClick);
@@ -193,6 +195,18 @@ cr.define('media_router', function() {
   }
 
   /**
+   * Reports the time it took for the user to select a sink to create a route
+   * after the list was popuated and shown.
+   *
+   * @param {{detail: {timeMs: number}}} data
+   * Paramters in |data|.detail:
+   *   timeMs - the time it took for the user to select a sink.
+   */
+  function onSinkClickTimeReported(data) {
+    media_router.browserApi.reportTimeToClickSink(data.detail.timeMs);
+  }
+
+  /**
    * Reports the current sink count.
    * Called 3 seconds after the dialog is initially opened.
    *
diff --git a/chrome/browser/resources/media_router/media_router_ui_interface.js b/chrome/browser/resources/media_router/media_router_ui_interface.js
index 4639335..c160475 100644
--- a/chrome/browser/resources/media_router/media_router_ui_interface.js
+++ b/chrome/browser/resources/media_router/media_router_ui_interface.js
@@ -212,6 +212,16 @@ cr.define('media_router.browserApi', function() {
   }
 
   /**
+   * Reports the time it took for the user to select a sink after the sink list
+   * is populated and shown.
+   *
+   * @param {number} timeMs
+   */
+  function reportTimeToClickSink(timeMs) {
+    chrome.send('reportTimeToClickSink', [timeMs]);
+  }
+
+  /**
    * Requests data to initialize the WebUI with.
    * The data will be returned via media_router.ui.setInitialData.
    */
@@ -243,6 +253,7 @@ cr.define('media_router.browserApi', function() {
     reportNavigateToView: reportNavigateToView,
     reportSelectedCastMode: reportSelectedCastMode,
     reportSinkCount: reportSinkCount,
+    reportTimeToClickSink: reportTimeToClickSink,
     requestInitialData: requestInitialData,
     requestRoute: requestRoute,
   };
diff --git a/chrome/browser/ui/webui/media_router/media_router_webui_message_handler.cc b/chrome/browser/ui/webui/media_router/media_router_webui_message_handler.cc
index f0c8a2e..79ab56a 100644
--- a/chrome/browser/ui/webui/media_router/media_router_webui_message_handler.cc
+++ b/chrome/browser/ui/webui/media_router/media_router_webui_message_handler.cc
@@ -40,6 +40,7 @@ const char kReportInitialState[] = "reportInitialState";
 const char kReportNavigateToView[] = "reportNavigateToView";
 const char kReportSelectedCastMode[] = "reportSelectedCastMode";
 const char kReportSinkCount[] = "reportSinkCount";
+const char kReportTimeToClickSink[] = "reportTimeToClickSink";
 const char kOnInitialDataReceived[] = "onInitialDataReceived";
 
 // JS function names.
@@ -293,6 +294,10 @@ void MediaRouterWebUIMessageHandler::RegisterMessages() {
       base::Bind(&MediaRouterWebUIMessageHandler::OnReportSinkCount,
                  base::Unretained(this)));
   web_ui()->RegisterMessageCallback(
+      kReportTimeToClickSink,
+      base::Bind(&MediaRouterWebUIMessageHandler::OnReportTimeToClickSink,
+                 base::Unretained(this)));
+  web_ui()->RegisterMessageCallback(
       kOnInitialDataReceived,
       base::Bind(&MediaRouterWebUIMessageHandler::OnInitialDataReceived,
                  base::Unretained(this)));
@@ -551,6 +556,18 @@ void MediaRouterWebUIMessageHandler::OnReportSinkCount(
   UMA_HISTOGRAM_COUNTS_100("MediaRouter.Ui.Device.Count", sink_count);
 }
 
+void MediaRouterWebUIMessageHandler::OnReportTimeToClickSink(
+    const base::ListValue* args) {
+  DVLOG(1) << "OnReportTimeToClickSink";
+  double time_to_click;
+  if (!args->GetDouble(0, &time_to_click)) {
+    DVLOG(1) << "Unable to extract args.";
+    return;
+  }
+  UMA_HISTOGRAM_TIMES("MediaRouter.Ui.Action.StartLocal.Latency",
+                      base::TimeDelta::FromMillisecondsD(time_to_click));
+}
+
 void MediaRouterWebUIMessageHandler::OnInitialDataReceived(
     const base::ListValue* args) {
   DVLOG(1) << "OnInitialDataReceived";
diff --git a/chrome/browser/ui/webui/media_router/media_router_webui_message_handler.h b/chrome/browser/ui/webui/media_router/media_router_webui_message_handler.h
index 673be24..936a20d 100644
--- a/chrome/browser/ui/webui/media_router/media_router_webui_message_handler.h
+++ b/chrome/browser/ui/webui/media_router/media_router_webui_message_handler.h
@@ -64,6 +64,7 @@ class MediaRouterWebUIMessageHandler : public content::WebUIMessageHandler {
   void OnReportNavigateToView(const base::ListValue* args);
   void OnReportSelectedCastMode(const base::ListValue* args);
   void OnReportSinkCount(const base::ListValue* args);
+  void OnReportTimeToClickSink(const base::ListValue* args);
   void OnInitialDataReceived(const base::ListValue* args);
 
   // Performs an action for an Issue of |type|.
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index f4e0cc9..b49e196 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -19704,6 +19704,15 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="MediaRouter.Ui.Action.StartLocal.Latency" units="ms">
+  <owner>apacible@chromium.org</owner>
+  <summary>
+    Duration in milliseconds taken from the Media Router dialog showing the sink
+    list and being populated with at least one device to the user selecting a
+    device immediately after to create a new route.
+  </summary>
+</histogram>
+
 <histogram name="MediaRouter.Ui.Action.StartLocalPosition"
     enum="MediaRouterSinkPositionLabel">
   <owner>apacible@chromium.org</owner>