Move device/usb classes from the FILE thread to UI thread.

device/test/usb_test_gadget.h

 // Copyright 2014 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 DEVICE_TEST_USB_TEST_GADGET_H_
 #define DEVICE_TEST_USB_TEST_GADGET_H_
 
 #include <string>
 
 #include "base/macros.h"
+#include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 
+namespace base {
+class SingleThreadTaskRunner;
+}
+
 namespace device {
 
 class UsbDevice;
 
 class UsbTestGadget {
  public:
   enum Type {
     DEFAULT = 0,
     KEYBOARD,
     MOUSE,
     HID_ECHO,
     ECHO,
   };
 
   virtual ~UsbTestGadget() {}
 
   static bool IsTestEnabled();
-  static scoped_ptr<UsbTestGadget> Claim();
+  static scoped_ptr<UsbTestGadget> Claim(
+      scoped_refptr<base::SingleThreadTaskRunner> io_task_runner);
 
   virtual bool Unclaim() = 0;
   virtual bool Disconnect() = 0;
   virtual bool Reconnect() = 0;
   virtual bool SetType(Type type) = 0;
 
   virtual UsbDevice* GetDevice() const = 0;
-  virtual const std::string& GetSerialNumber() const = 0;
 
  protected:
   UsbTestGadget() {}
 
  private:
   DISALLOW_COPY_AND_ASSIGN(UsbTestGadget);
 };
 
 }  // namespace device
 
 #endif  // DEVICE_TEST_USB_TEST_GADGET_H_