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

public/platform/WebPlatformEventType.h

Index: public/platform/WebPlatformEventType.h
diff --git a/public/platform/WebPlatformEventType.h b/public/platform/WebPlatformEventType.h
new file mode 100644
index 0000000000000000000000000000000000000000..2fd577c2301cc932ed649b465deead719101ceb0
--- /dev/null
+++ b/public/platform/WebPlatformEventType.h
@@ -0,0 +1,20 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef WebPlatformEventType_h
+#define WebPlatformEventType_h
+
+namespace blink {
+
+enum WebPlatformEventType {
+    WebPlatformEventDeviceMotion,
+    WebPlatformEventDeviceOrientation,
+    WebPlatformEventDeviceLight,
+    WebPlatformEventBattery,
+    WebPlatformEventGamepad,
+};
+
+} // namespace blink
+
+#endif // WebPlatformEventType_h