Add USBConnectionEvent to webusb module.

Source/modules/webusb/USBConnectionEvent.h

+// Copyright 2015 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 USBConnectionEvent_h
+#define USBConnectionEvent_h
+
+#include "modules/EventModules.h"
+#include "platform/heap/Handle.h"
+
+namespace blink {
+
+class USBConnectionEventInit;
+class USBDevice;
+
+class USBConnectionEvent final : public Event {
+    DEFINE_WRAPPERTYPEINFO();
+public:
+    static USBConnectionEvent* create(const AtomicString& type, const USBConnectionEventInit&);
+    static USBConnectionEvent* create(const AtomicString& type, USBDevice*);
+
+    USBConnectionEvent(const AtomicString& type, const USBConnectionEventInit&);
+    USBConnectionEvent(const AtomicString& type, USBDevice*);
+
+    USBDevice* device() const { return m_device; }
+
+    DECLARE_VIRTUAL_TRACE();
+
+private:
+    PersistentWillBeMember<USBDevice> m_device;
+};
+
+} // namespace blink
+
+#endif // USBConnectionEvent_h