WebUSB bindings part 3

Source/modules/webusb/USBInterface.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/USBInterface.h"
+
+#include "bindings/core/v8/ExceptionState.h"
+#include "modules/webusb/USBConfiguration.h"
+
+namespace blink {
+
+USBInterface* USBInterface::create(const USBConfiguration* configuration, size_t interfaceIndex)
+{
+    return new USBInterface(configuration, interfaceIndex);
+}
+
+USBInterface* USBInterface::create(const USBConfiguration* configuration, size_t interfaceIndex, ExceptionState& exceptionState)
+{
+    if (interfaceIndex < configuration->info().interfaces.size())

[Reilly Grant (use Gerrit), 2015/08/03 23:00:50]

Since this constructor will be called from scripts without insight into the set
of interface descriptors read from the device this should take an
interfaceNumber and validate it before returning.

[Ken Rockot(use gerrit already), 2015/08/04 00:51:25]

Done.

+        return new USBInterface(configuration, interfaceIndex);
+    exceptionState.throwRangeError("Invalid interface index.");
+    return nullptr;
+}
+
+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;
+}
+
+DEFINE_TRACE(USBInterface)
+{
+    visitor->trace(m_configuration);
+}
+
+} // namespace blink