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

public/platform/WebDeviceLightListener.h

Index: public/platform/WebDeviceLightListener.h
diff --git a/public/platform/WebDeviceLightListener.h b/public/platform/WebDeviceLightListener.h
index 4b40842c89800358956b3491b2488b42a31c0e3f..26dc1ab195ef02a8d6268a407ee1eb84facd848a 100644
--- a/public/platform/WebDeviceLightListener.h
+++ b/public/platform/WebDeviceLightListener.h
@@ -5,9 +5,11 @@
 #ifndef WebDeviceLightListener_h
 #define WebDeviceLightListener_h
 
+#include "WebPlatformEventListener.h"
+
 namespace blink {
 
-class WebDeviceLightListener {
+class WebDeviceLightListener : public WebPlatformEventListener {
 public:
     // This method is called every time new device light data is available.
     virtual void didChangeDeviceLight(double) = 0;