Introduce PlatformEvent to handle Device events, Battery events and Gamepad events.

Source/modules/device_light/DeviceLightDispatcher.cpp

Index: Source/modules/device_light/DeviceLightDispatcher.cpp
diff --git a/Source/modules/device_light/DeviceLightDispatcher.cpp b/Source/modules/device_light/DeviceLightDispatcher.cpp
index 68da4d0b8e3ff2772df581f85c0076bc7af64390..05870d49123db6b7986d88311f654abd853810a3 100644
--- a/Source/modules/device_light/DeviceLightDispatcher.cpp
+++ b/Source/modules/device_light/DeviceLightDispatcher.cpp
@@ -27,12 +27,12 @@ DeviceLightDispatcher::~DeviceLightDispatcher()
 
 void DeviceLightDispatcher::startListening()
 {
-    blink::Platform::current()->setDeviceLightListener(this);
+    blink::Platform::current()->startListening(WebPlatformEventDeviceLight, this);
 }
 
 void DeviceLightDispatcher::stopListening()
 {
-    blink::Platform::current()->setDeviceLightListener(0);
+    blink::Platform::current()->stopListening(WebPlatformEventDeviceLight);
     m_lastDeviceLightData = -1;
 }