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

public/platform/WebPlatformEventListener.h

Index: public/platform/WebPlatformEventListener.h
diff --git a/Source/core/frame/NavigatorCPU.h b/public/platform/WebPlatformEventListener.h
similarity index 54%
copy from Source/core/frame/NavigatorCPU.h
copy to public/platform/WebPlatformEventListener.h
index 84d4f58244d3d832e20d703fd8a9d09cf344b303..7a7b901f5fd269aa23199298fc52a00501188dd6 100644
--- a/Source/core/frame/NavigatorCPU.h
+++ b/public/platform/WebPlatformEventListener.h
@@ -2,16 +2,16 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef NavigatorCPU_h
-#define NavigatorCPU_h
+#ifndef WebPlatformEventListener_h
+#define WebPlatformEventListener_h
 
 namespace blink {
 
-class NavigatorCPU {
+class WebPlatformEventListener {
 public:
-    unsigned hardwareConcurrency() const;
+    virtual ~WebPlatformEventListener() { }
 };
 
 } // namespace blink
 
-#endif // NavigatorCPU_h
+#endif // WebPlatformEventListener_h