Manage UsbService lifetime in DeviceClient implementations.

device/test/test_device_client.h

+// 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 "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
+#include "device/core/device_client.h"
+
+namespace base {
+class SingleThreadTaskRunner;
+}
+
+namespace device {
+
+class HidService;
+class UsbService;
+
+class TestDeviceClient : public DeviceClient {
+ public:
+  TestDeviceClient(scoped_refptr<base::SingleThreadTaskRunner> task_runner);
+  ~TestDeviceClient() override;
+
+ private:
+  HidService* GetHidService() override;
+  UsbService* GetUsbService() override;
+
+  scoped_ptr<UsbService> usb_service_;
+  scoped_refptr<base::SingleThreadTaskRunner> blocking_task_runner_;
+};
+
+}  // namespace device