Add WebUSB bindings and client interface

Source/modules/webusb/USBAlternateInterface.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 USBAlternateInterface_h
+#define USBAlternateInterface_h
+
+#include "bindings/core/v8/ScriptWrappable.h"
+#include "platform/heap/Heap.h"
+#include "public/platform/modules/webusb/WebUSBDeviceInfo.h"
+
+namespace blink {
+
+class USBEndpoint;
+class USBInterface;
+
+class USBAlternateInterface
+    : public GarbageCollected<USBAlternateInterface>
+    , public ScriptWrappable {
+    DEFINE_WRAPPERTYPEINFO();
+public:
+    static USBAlternateInterface* create(const USBInterface*, size_t alternateIndex);

[Reilly Grant (use Gerrit), 2015/07/28 22:51:42]

alternateIndex != alternateSetting so be careful if this method is exposed to
the web.

[Ken Rockot(use gerrit already), 2015/07/28 23:21:39]

Acknowledged. We may want to change constructors to use configuration values,
interface numbers, alternate settings, and endpoint numbers. For now I went with
indexes, but we can always change it.

+
+    USBAlternateInterface(const USBInterface*, size_t alternateIndex);
+
+    const WebUSBDeviceInfo::AlternateInterface& info() const;
+
+    uint8_t alternateSetting() const;
+    uint8_t interfaceClass() const;
+    uint8_t interfaceSubclass() const;
+    uint8_t interfaceProtocol() const;
+    String interfaceName() const;
+    HeapVector<Member<USBEndpoint>> endpoints() const;
+
+    DECLARE_TRACE();
+
+private:
+    Member<const USBInterface> m_interface;
+    size_t m_alternateIndex;
+};
+
+} // namespace blink
+
+#endif // USBAlternateInterface_h