Remove (Native)Widget::StackBelow().

ui/views/widget/desktop_aura/desktop_native_widget_aura.cc

 // Copyright (c) 2012 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/views/widget/desktop_aura/desktop_native_widget_aura.h"
 
 #include "base/bind.h"
 #include "base/macros.h"
 #include "base/trace_event/trace_event.h"
 #include "build/build_config.h"
@@ skipping 671 matching lines @@
 void DesktopNativeWidgetAura::StackAbove(gfx::NativeView native_view) {
   if (content_window_)
     desktop_window_tree_host_->StackAbove(native_view);
 }
 
 void DesktopNativeWidgetAura::StackAtTop() {
   if (content_window_)
     desktop_window_tree_host_->StackAtTop();
 }
 
-void DesktopNativeWidgetAura::StackBelow(gfx::NativeView native_view) {
-}
-
 void DesktopNativeWidgetAura::SetShape(std::unique_ptr<SkRegion> shape) {
   if (content_window_)
     desktop_window_tree_host_->SetShape(std::move(shape));
 }
 
 void DesktopNativeWidgetAura::Close() {
   if (!content_window_)
     return;
 
   content_window_->SuppressPaint();
@@ skipping 484 matching lines @@
   if (cursor_reference_count_ == 0) {
     // We are the last DesktopNativeWidgetAura instance, and we are responsible
     // for cleaning up |cursor_manager_|.
     delete cursor_manager_;
     native_cursor_manager_ = NULL;
     cursor_manager_ = NULL;
   }
 }
 
 }  // namespace views