Add WebUSB bindings and client interface [part 1]

Source/modules/webusb/NavigatorUSB.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 NavigatorUSB_h
+#define NavigatorUSB_h
+
+#include "platform/Supplementable.h"
+#include "platform/heap/Handle.h"
+
+namespace blink {
+
+class Navigator;
+class USB;
+
+class NavigatorUSB final
+    : public GarbageCollected<NavigatorUSB>
+    , public HeapSupplement<Navigator> {
+    USING_GARBAGE_COLLECTED_MIXIN(NavigatorUSB);
+public:
+    // Gets, or creates, NavigatorUSB supplement on Navigator.
+    // See platform/Supplementable.h
+    static NavigatorUSB& from(Navigator&);
+
+    static USB* usb(Navigator&);
+    USB* usb();
+
+    DECLARE_TRACE();
+
+private:
+    explicit NavigatorUSB(Navigator&);
+    static const char* supplementName();
+
+    Member<USB> m_usb;
+};
+
+} // namespace blink
+
+#endif // NavigatorUSB_h