Bug 948139 - Use UITelemetry to capture clicks on the 'switch to desktop' appbar item. r=mbrubeck

browser/metro/base/content/appbar.js

@@ -25,6 +25,14 @@ var Appbar = {
 
     // tilegroup selection events for all modules get bubbled up
     window.addEventListener("selectionchange", this, false);
+
+    // gather appbar telemetry data
+    try {
+      UITelemetry.addSimpleMeasureFunction("metro-appbar",
+                                           this.getAppbarMeasures.bind(this));
+    } catch (ex) {
+      // swallow exception that occurs if metro-appbar measure is already set up
+    }
   },
 
   handleEvent: function Appbar_handleEvent(aEvent) {
@@ -149,6 +157,7 @@ var Appbar = {
       getService(Components.interfaces.nsIAppStartup);
 
     Services.prefs.setBoolPref('browser.sessionstore.resume_session_once', true);
+    this._incrementCountableEvent("switch-to-desktop-button");
     appStartup.quit(Components.interfaces.nsIAppStartup.eAttemptQuit |
                     Components.interfaces.nsIAppStartup.eRestart);
   },
@@ -273,6 +282,22 @@ var Appbar = {
     }
   },
 
+  // track certain appbar events and interactions for the UITelemetry probe
+  _countableEvents: {},
+
+  _incrementCountableEvent: function(aName) {
+    if (!(aName in this._countableEvents)) {
+      this._countableEvents[aName] = 0;
+    }
+    this._countableEvents[aName]++;
+  },
+
+  getAppbarMeasures: function() {
+    return {
+      countableEvents: this._countableEvents
+    };
+  },
+
   _updatePinButton: function() {
     this.pinButton.checked = Browser.isSitePinned();
   },
@@ -282,4 +307,5 @@ var Appbar = {
       this.starButton.checked = isStarred;
     }.bind(this));
   },
+
 };

browser/metro/base/content/browser-scripts.js

@@ -54,6 +54,8 @@ XPCOMUtils.defineLazyModuleGetter(this, "Task",
 XPCOMUtils.defineLazyModuleGetter(this, "OS",
                                   "resource://gre/modules/osfile.jsm");
 
+XPCOMUtils.defineLazyModuleGetter(this, "UITelemetry",
+                                  "resource://gre/modules/UITelemetry.jsm");
 /*
  * Services
  */