Remove unused |context| from GetDefaultParent().

ui/aura/test/test_window_parenting_client.cc

 // Copyright (c) 2013 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.
 
 #include "ui/aura/test/test_window_parenting_client.h"
 
 #include "ui/aura/window.h"
 
 namespace aura {
 namespace test {
 
 TestWindowParentingClient::TestWindowParentingClient(Window* root_window)
     : root_window_(root_window) {
   client::SetWindowParentingClient(root_window_, this);
 }
 
 TestWindowParentingClient::~TestWindowParentingClient() {
   client::SetWindowParentingClient(root_window_, nullptr);
 }
 
-Window* TestWindowParentingClient::GetDefaultParent(Window* context,
-                                                    Window* window,
+Window* TestWindowParentingClient::GetDefaultParent(Window* window,
                                                     const gfx::Rect& bounds) {
   return root_window_;
 }
 
 }  // namespace test
 }  // namespace aura