Add WebUSB bindings and client interface

Source/modules/webusb/USBInterface.cpp

Index: Source/modules/webusb/USBInterface.cpp
diff --git a/Source/modules/webusb/USBInterface.cpp b/Source/modules/webusb/USBInterface.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..ca809010d6ea794823089e06120c130cd48bf33c
--- /dev/null
+++ b/Source/modules/webusb/USBInterface.cpp
@@ -0,0 +1,50 @@
+// 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/USBInterface.h"
+
+#include "modules/webusb/USBAlternateInterface.h"
+#include "modules/webusb/USBConfiguration.h"
+
+namespace blink {
+
+// static
+USBInterface* USBInterface::create(const USBConfiguration* configuration, size_t interfaceIndex)
+{
+    return new USBInterface(configuration, interfaceIndex);
+}
+
+USBInterface::USBInterface(const USBConfiguration* configuration, size_t interfaceIndex)
+    : m_configuration(configuration)
+    , m_interfaceIndex(interfaceIndex)
+{
+}
+
+const WebUSBDeviceInfo::Interface& USBInterface::info() const
+{
+    const WebUSBDeviceInfo::Configuration& configInfo = m_configuration->info();
+    ASSERT(m_interfaceIndex < configInfo.interfaces.size());
+    return configInfo.interfaces[m_interfaceIndex];
+}
+
+uint8_t USBInterface::interfaceNumber() const
+{
+    return info().interfaceNumber;
+}
+
+HeapVector<Member<USBAlternateInterface>> USBInterface::alternates() const
+{
+    HeapVector<Member<USBAlternateInterface>> alternates;
+    for (size_t i = 0; i < info().alternates.size(); ++i)
+        alternates.append(USBAlternateInterface::create(this, i));
+    return alternates;
+}
+
+DEFINE_TRACE(USBInterface)
+{
+    visitor->trace(m_configuration);
+}
+
+} // namespace blink