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

Source/modules/battery/BatteryDispatcher.h

Index: Source/modules/battery/BatteryDispatcher.h
diff --git a/Source/modules/battery/BatteryDispatcher.h b/Source/modules/battery/BatteryDispatcher.h
index 6fdf38f7ead9c06f2f8d4db121a0fdd572549cbd..90c49825b42fbd9fe453de3b4e4013b7b9c07470 100644
--- a/Source/modules/battery/BatteryDispatcher.h
+++ b/Source/modules/battery/BatteryDispatcher.h
@@ -5,7 +5,7 @@
 #ifndef BatteryDispatcher_h
 #define BatteryDispatcher_h
 
-#include "core/frame/DeviceEventDispatcherBase.h"
+#include "core/frame/PlatformEventDispatcher.h"
 #include "modules/battery/BatteryManager.h"
 #include "modules/battery/BatteryStatus.h"
 #include "public/platform/WebBatteryStatusListener.h"
@@ -16,7 +16,7 @@ class WebBatteryStatus;
 
 namespace blink {
 
-class BatteryDispatcher FINAL : public DeviceEventDispatcherBase, public blink::WebBatteryStatusListener {
+class BatteryDispatcher FINAL : public PlatformEventDispatcher, public blink::WebBatteryStatusListener {
 public:
     static BatteryDispatcher& instance();
     virtual ~BatteryDispatcher();
@@ -29,7 +29,7 @@ public:
 private:
     BatteryDispatcher();
 
-    // Inherited from DeviceEventDispatcherBase.
+    // Inherited from PlatformEventDispatcher.
     virtual void startListening() OVERRIDE;
     virtual void stopListening() OVERRIDE;