Add USBConnectionEvent to webusb module.

Source/modules/webusb/USBConnectionEvent.cpp

+// 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.
+
+#include "config.h"
+#include "modules/webusb/USBConnectionEvent.h"
+
+#include "modules/webusb/USBConnectionEventInit.h"
+#include "modules/webusb/USBDevice.h"
+
+namespace blink {
+
+USBConnectionEvent* USBConnectionEvent::create(const AtomicString& type, const USBConnectionEventInit& initializer)
+{
+    return new USBConnectionEvent(type, initializer);
+}
+
+USBConnectionEvent* USBConnectionEvent::create(const AtomicString& type, USBDevice* device)
+{
+    return new USBConnectionEvent(type, device);
+}
+
+USBConnectionEvent::USBConnectionEvent(const AtomicString& type, const USBConnectionEventInit& initializer)
+    : Event(type, initializer)
+    , m_device(nullptr)
+{
+    if (initializer.hasDevice())
+        m_device = initializer.device();
+}
+
+USBConnectionEvent::USBConnectionEvent(const AtomicString& type, USBDevice* device)
+    : Event(type, false, false)
+    , m_device(device)
+{
+}
+
+DEFINE_TRACE(USBConnectionEvent)
+{
+    visitor->trace(m_device);
+    Event::trace(visitor);
+}
+
+} // namespace blink