Bug 975667 - gecko: hal: gonk: Emit battery level/charging notificati…

…on. r=dhylands

The battery level and charging flag is now emitted from nsIObserverService
via the "gonkhal-battery-notifier" topic.  This can be useful to XPCOM
components that are not statically linked to Gecko.

The notification data is a IPropertyBag2 object.

Change-Id: Ia7b1faf3b66c19d6551d71ad554fd361c2614a22

hal/gonk/GonkHal.cpp

@@ -66,6 +66,7 @@
 #include "nsXULAppAPI.h"
 #include "OrientationObserver.h"
 #include "UeventPoller.h"
+#include "nsIWritablePropertyBag2.h"
 #include <algorithm>
 
 #define LOG(args...)  __android_log_print(ANDROID_LOG_INFO, "Gonk", args)
@@ -290,6 +291,25 @@ class BatteryUpdater : public nsRunnable {
     hal_impl::SetLight(hal::eHalLightID_Battery, aConfig);
 
     hal::NotifyBatteryChange(info);
+
+    {
+      // bug 975667
+      // Gecko gonk hal is required to emit battery charging/level notification via nsIObserverService.
+      // This is useful for XPCOM components that are not statically linked to Gecko and cannot call
+      // hal::EnableBatteryNotifications
+      nsCOMPtr<nsIObserverService> obsService = mozilla::services::GetObserverService();
+      nsCOMPtr<nsIWritablePropertyBag2> propbag =
+        do_CreateInstance("@mozilla.org/hash-property-bag;1");
+      if (obsService && propbag) {
+        propbag->SetPropertyAsBool(NS_LITERAL_STRING("charging"),
+                                   info.charging());
+        propbag->SetPropertyAsDouble(NS_LITERAL_STRING("level"),
+                                   info.level());
+
+        obsService->NotifyObservers(propbag, "gonkhal-battery-notifier", nullptr);
+      }
+    }
+
     return NS_OK;
   }
 };