Cleanup after transition to new attestation dbus methods.

The methods with the 'New' suffix are temporary and will soon be
removed.

BUG=chromium:243605
TEST=manual

Review URL: https://codereview.chromium.org/213413009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@260428 0039d316-1c4b-4281-b951-d872f2087c98
  void OnStringMethod(const StringDBusMethodCallback& callback,
                      dbus::Response* response) {
    if (!response) {
      callback.Run(DBUS_METHOD_CALL_FAILURE, std::string());
      return;
    }
    dbus::MessageReader reader(response);
    std::string result;
    if (!reader.PopString(&result)) {
      callback.Run(DBUS_METHOD_CALL_FAILURE, std::string());
      return;
    }
    callback.Run(DBUS_METHOD_CALL_SUCCESS, result);
  }

  void OnStringMethod(const StringDBusMethodCallback& callback,
                      dbus::Response* response) {
    if (!response) {
      callback.Run(DBUS_METHOD_CALL_FAILURE, std::string());
      return;
    }
    dbus::MessageReader reader(response);
    std::string result;
    if (!reader.PopString(&result)) {
      callback.Run(DBUS_METHOD_CALL_FAILURE, std::string());
      return;
    }
    callback.Run(DBUS_METHOD_CALL_SUCCESS, result);
  }
