[DeviceService] Add service tests for VibrationManager.

device/vibration/vibration_manager_impl.h

Index: device/vibration/vibration_manager_impl.h
diff --git a/device/vibration/vibration_manager_impl.h b/device/vibration/vibration_manager_impl.h
index de9a0617aac17aa1d5dd93dfbd754cbb548a1644..75260a20ed16cf1e938717fbc21ed1914639d35d 100644
--- a/device/vibration/vibration_manager_impl.h
+++ b/device/vibration/vibration_manager_impl.h
@@ -14,6 +14,9 @@ class VibrationManagerImpl {
  public:
   DEVICE_VIBRATION_EXPORT static void Create(
       mojo::InterfaceRequest<mojom::VibrationManager> request);
+
+  DEVICE_VIBRATION_EXPORT static int64_t milli_seconds_for_testing_;
+  DEVICE_VIBRATION_EXPORT static bool cancelled_for_testing_;
 };
 
 }  // namespace device