Remove BrowserThread dependency from usb_service.

extensions/shell/browser/shell_device_client.h

Index: extensions/shell/browser/shell_device_client.h
diff --git a/extensions/shell/browser/shell_device_client.h b/extensions/shell/browser/shell_device_client.h
new file mode 100644
index 0000000000000000000000000000000000000000..4a1089e52bed8a28428ba08a279b86b5c6405b76
--- /dev/null
+++ b/extensions/shell/browser/shell_device_client.h
@@ -0,0 +1,26 @@
+// 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 EXTENSIONS_SHELL_BROWSER_SHELL_DEVICE_CLIENT_H_
+#define EXTENSIONS_SHELL_BROWSER_SHELL_DEVICE_CLIENT_H_
+
+#include "device/common/device_client.h"
+
+#include "base/compiler_specific.h"
+
+namespace extensions {
+
+// Implementation of device::DeviceClient that returns //device API service
+// singletons appropriate for use within app shell.
+class ShellDeviceClient : device::DeviceClient {
+ public:
+  ShellDeviceClient();
+  virtual ~ShellDeviceClient();
+
+  virtual usb_service::UsbService* GetUsbService() OVERRIDE;
+};
+
+}
+
+#endif  // EXTENSIONS_SHELL_BROWSER_SHELL_DEVICE_CLIENT_H_