Replace device_sensor browsertest by service unittest.

services/device/device_service_test_base.h

 // Copyright 2017 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 SERVICES_DEVICE_DEVICE_SERVICE_TEST_BASE_H_
 #define SERVICES_DEVICE_DEVICE_SERVICE_TEST_BASE_H_
 
 #include "base/macros.h"
+#include "base/threading/thread.h"
 #include "services/service_manager/public/cpp/service_test.h"
 
 namespace device {
 
 // Base class responsible to setup Device Service for test.
 class DeviceServiceTestBase : public service_manager::test::ServiceTest {
  public:
   DeviceServiceTestBase();
   ~DeviceServiceTestBase() override;
 
  private:
   // service_manager::test::ServiceTest:
   std::unique_ptr<service_manager::Service> CreateService() override;
 
+  base::Thread io_thread_;
+
   DISALLOW_COPY_AND_ASSIGN(DeviceServiceTestBase);
 };
 
 }  // namespace device
 
 #endif  // SERVICES_DEVICE_DEVICE_SERVICE_TEST_BASE_H_