Manage UsbService lifetime in DeviceClient implementations.

device/test/usb_test_gadget_impl.cc

Index: device/test/usb_test_gadget_impl.cc
diff --git a/device/test/usb_test_gadget_impl.cc b/device/test/usb_test_gadget_impl.cc
index a94cb763804cc5c092bc65b3760266ef7527a3ba..0222ab32f5714348ae41422781c3c9273f5d70fd 100644
--- a/device/test/usb_test_gadget_impl.cc
+++ b/device/test/usb_test_gadget_impl.cc
@@ -23,6 +23,7 @@
 #include "base/strings/utf_string_conversions.h"
 #include "base/thread_task_runner_handle.h"
 #include "base/time/time.h"
+#include "device/core/device_client.h"
 #include "device/usb/usb_device.h"
 #include "device/usb/usb_device_handle.h"
 #include "device/usb/usb_service.h"
@@ -192,7 +193,7 @@ class UsbGadgetFactory : public UsbService::Observer,
  public:
   UsbGadgetFactory(scoped_refptr<base::SingleThreadTaskRunner> io_task_runner)
       : observer_(this), weak_factory_(this) {
-    usb_service_ = UsbService::GetInstance(io_task_runner);
+    usb_service_ = DeviceClient::Get()->GetUsbService();
     request_context_getter_ = new URLRequestContextGetter(io_task_runner);
 
     static uint32 next_session_id;