Remove BrowserThread dependency from usb_service.

components/usb_service/usb_device_impl.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 COMPONENTS_USB_SERVICE_USB_DEVICE_IMPL_H_
 #define COMPONENTS_USB_SERVICE_USB_DEVICE_IMPL_H_
 
 #include <vector>
 
 #include "base/basictypes.h"
 #include "base/callback.h"
 #include "base/threading/thread_checker.h"
 #include "components/usb_service/usb_device.h"
 
 struct libusb_device;
 struct libusb_config_descriptor;
 
+namespace base {
+class SingleThreadTaskRunner;
+}
+
 namespace usb_service {
 
 class UsbDeviceHandleImpl;
 class UsbContext;
 
 typedef libusb_device* PlatformUsbDevice;
 typedef libusb_config_descriptor* PlatformUsbConfigDescriptor;
 
 class UsbDeviceImpl : public UsbDevice {
  public:
 // UsbDevice implementation:
 #if defined(OS_CHROMEOS)
   virtual void RequestUsbAccess(
       int interface_id,
       const base::Callback<void(bool success)>& callback) OVERRIDE;
 #endif  // OS_CHROMEOS
   virtual scoped_refptr<UsbDeviceHandle> Open() OVERRIDE;
   virtual bool Close(scoped_refptr<UsbDeviceHandle> handle) OVERRIDE;
   virtual scoped_refptr<UsbConfigDescriptor> ListInterfaces() OVERRIDE;
 
  protected:
   friend class UsbServiceImpl;
 
   // Called by UsbServiceImpl only;
   UsbDeviceImpl(scoped_refptr<UsbContext> context,
+                scoped_refptr<base::SingleThreadTaskRunner> ui_task_runner,
                 PlatformUsbDevice platform_device,
                 uint16 vendor_id,
                 uint16 product_id,
                 uint32 unique_id);
 
   virtual ~UsbDeviceImpl();
 
   // Called only be UsbService.
   void OnDisconnect();
 
  private:
   base::ThreadChecker thread_checker_;
   PlatformUsbDevice platform_device_;
 
   // Retain the context so that it will not be released before UsbDevice.
   scoped_refptr<UsbContext> context_;
 
   // Opened handles.
   typedef std::vector<scoped_refptr<UsbDeviceHandleImpl> > HandlesVector;
   HandlesVector handles_;
 
+  // Reference to the UI thread for permission-broker calls.
+  scoped_refptr<base::SingleThreadTaskRunner> ui_task_runner_;
+
   DISALLOW_COPY_AND_ASSIGN(UsbDeviceImpl);
 };
 
 }  // namespace usb_service
 
 #endif  // COMPONENTS_USB_SERVICE_USB_DEVICE_IMPL_H_