Bug 1259335 - Part 1.5: Collect use count telemetry for Battery Status API. r=baku

dom/base/Navigator.cpp

@@ -204,6 +204,7 @@ Navigator::Init()
 
 Navigator::Navigator(nsPIDOMWindowInner* aWindow)
   : mWindow(aWindow)
+  , mBatteryTelemetryReported(false)
 {
   MOZ_ASSERT(aWindow->IsInnerWindow(), "Navigator must get an inner window!");
 }
@@ -307,6 +308,7 @@ Navigator::Invalidate()
   }
 
   mBatteryPromise = nullptr;
+  mBatteryTelemetryReported = false;
 
 #ifdef MOZ_B2G_FM
   if (mFMRadio) {
@@ -1587,6 +1589,10 @@ Navigator::GetBattery(ErrorResult& aRv)
   }
   mBatteryPromise = batteryPromise;
 
+  // We just initialized mBatteryPromise, so we know this is the first time
+  // this page has accessed navigator.getBattery(). 1 = navigator.getBattery()
+  Telemetry::Accumulate(Telemetry::BATTERY_STATUS_COUNT, 1);
+
   if (!mBatteryManager) {
     mBatteryManager = new battery::BatteryManager(mWindow);
     mBatteryManager->Init();

dom/base/Navigator.h

@@ -403,6 +403,8 @@ private:
 
   nsTArray<RefPtr<Promise> > mVRGetDevicesPromises;
   nsTArray<uint32_t> mRequestedVibrationPattern;
+
+  bool mBatteryTelemetryReported;
 };
 
 } // namespace dom

toolkit/components/telemetry/Histograms.json

@@ -100,6 +100,14 @@
     "n_values": 21,
     "description": "Maximum number of concurrent threads reached during a given download session"
   },
+  "BATTERY_STATUS_COUNT": {
+    "alert_emails": ["cpeterson@mozilla.com"],
+    "bug_numbers": [1259335],
+    "expires_in_version": "52",
+    "kind": "enumerated",
+    "n_values": 10,
+    "description": "Number of pages that use the Battery Status API: 0=navigator.battery, 1=navigator.getBattery()"
+  },
   "BLOCKLIST_SYNC_FILE_LOAD": {
     "alert_emails": ["rvitillo@mozilla.com"],
     "expires_in_version": "35",