Add WebUSB bindings and client interface [part 1]

Source/modules/webusb/USB.cpp

Index: Source/modules/webusb/USB.cpp
diff --git a/Source/modules/webusb/USB.cpp b/Source/modules/webusb/USB.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..fda4300f7861a066f75dd41f2ba93718a489ed85
--- /dev/null
+++ b/Source/modules/webusb/USB.cpp
@@ -0,0 +1,31 @@
+// 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/USB.h"
+
+#include "modules/webusb/USBDeviceEnumerationOptions.h"
+#include "modules/webusb/USBDeviceFilter.h"
+#include "public/platform/modules/webusb/WebUSBClient.h"
+#include "public/platform/modules/webusb/WebUSBDeviceEnumerationOptions.h"
+#include "public/platform/modules/webusb/WebUSBDeviceFilter.h"
+
+namespace blink {
+
+USB::USB(LocalFrame& frame)
+    : m_controller(USBController::from(frame))
+{
+}
+
+ScriptPromise USB::getDevices(ScriptState* scriptState, const USBDeviceEnumerationOptions& options)
+{
+    ASSERT_NOT_REACHED();
+}
+
+DEFINE_TRACE(USB)
+{
+    visitor->trace(m_controller);
+}
+
+} // namespace blink