Add simple mash context menu support.

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"
+#include "ash/mus/context_menu_mus.h"
 #include "ash/mus/shelf_delegate_mus.h"
 #include "ash/session/session_state_delegate.h"
 #include "ash/system/tray/default_system_tray_delegate.h"
 #include "base/strings/string16.h"
 #include "components/user_manager/user_info_impl.h"
 #include "ui/gfx/image/image.h"
 
 namespace ash {
 namespace sysui {
 
@@ skipping 67 matching lines @@
     return MEDIA_CAPTURE_NONE;
   }
 
  private:
   DISALLOW_COPY_AND_ASSIGN(MediaDelegateStub);
 };
 
 }  // namespace
 
 ShellDelegateMus::ShellDelegateMus() {}
+
 ShellDelegateMus::~ShellDelegateMus() {}
 
 bool ShellDelegateMus::IsFirstRunAfterBoot() const {
   NOTIMPLEMENTED();
   return false;
 }
 
 bool ShellDelegateMus::IsIncognitoAllowed() const {
   NOTIMPLEMENTED();
   return false;
@@ skipping 84 matching lines @@
   return nullptr;
 }
 
 MediaDelegate* ShellDelegateMus::CreateMediaDelegate() {
   NOTIMPLEMENTED() << " Using a stub MediaDelegate implementation";
   return new MediaDelegateStub;
 }
 
 ui::MenuModel* ShellDelegateMus::CreateContextMenu(ash::Shelf* shelf,
                                                    const ShelfItem* item) {
-  NOTIMPLEMENTED();
-  return nullptr;
+  return new ContextMenuMus(shelf);
 }
 
 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