Pass shelf instances, not root windows, for ash context menus.

ash/mus/shell_delegate_mus.cc

 // Copyright 2016 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 "ash/mus/shell_delegate_mus.h"
 
 #include "ash/default_accessibility_delegate.h"
 #include "ash/default_user_wallpaper_delegate.h"
 #include "ash/gpu_support_stub.h"
 #include "ash/media_delegate.h"
@@ skipping 179 matching lines @@
 NewWindowDelegate* ShellDelegateMus::CreateNewWindowDelegate() {
   NOTIMPLEMENTED();
   return nullptr;
 }
 
 MediaDelegate* ShellDelegateMus::CreateMediaDelegate() {
   NOTIMPLEMENTED() << " Using a stub MediaDelegate implementation";
   return new MediaDelegateStub;
 }
 
-ui::MenuModel* ShellDelegateMus::CreateContextMenu(aura::Window* root_window,
+ui::MenuModel* ShellDelegateMus::CreateContextMenu(ash::Shelf* shelf,
                                                    const ShelfItem* item) {
   NOTIMPLEMENTED();
   return nullptr;
 }
 
 GPUSupport* ShellDelegateMus::CreateGPUSupport() {
   NOTIMPLEMENTED() << " Using a stub GPUSupport implementation";
   return new GPUSupportStub();
 }
 
 base::string16 ShellDelegateMus::GetProductName() const {
   NOTIMPLEMENTED();
   return base::string16();
 }
 
 gfx::Image ShellDelegateMus::GetDeprecatedAcceleratorImage() const {
   NOTIMPLEMENTED();
   return gfx::Image();
 }
 
 }  // namespace sysui
 }  // namespace ash