Move string descriptor getters from UsbDeviceHandle to UsbDevice.

device/hid/hid_connection_unittest.cc

Index: device/hid/hid_connection_unittest.cc
diff --git a/device/hid/hid_connection_unittest.cc b/device/hid/hid_connection_unittest.cc
index 5c67edf349e098f3d0947fae31b7a332ae47191f..113b27eae245df5a1a51ffce2d67fd1faa8cf733 100644
--- a/device/hid/hid_connection_unittest.cc
+++ b/device/hid/hid_connection_unittest.cc
@@ -100,7 +100,7 @@ class HidConnectionTest : public testing::Test {
     for (std::vector<HidDeviceInfo>::iterator it = devices.begin();
          it != devices.end();
          ++it) {
-      if (it->serial_number == test_gadget_->GetSerial()) {
+      if (it->serial_number == test_gadget_->GetSerialNumber()) {
         device_id_ = it->device_id;
         break;
       }