mash: Fix ash_sysui crash on startup due to missing AppListShower

ash/mus/shell_delegate_mus.h

 // 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.
 
 #ifndef ASH_MUS_SHELL_DELEGATE_MUS_H_
 #define ASH_MUS_SHELL_DELEGATE_MUS_H_
 
+#include <memory>
 #include <string>
 
 #include "ash/shell_delegate.h"
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 
 namespace keyboard {
 class KeyboardUI;
 }
 
@@ skipping 29 matching lines @@
   ash::AccessibilityDelegate* CreateAccessibilityDelegate() override;
   ash::NewWindowDelegate* CreateNewWindowDelegate() override;
   ash::MediaDelegate* CreateMediaDelegate() override;
   ui::MenuModel* CreateContextMenu(ash::Shelf* shelf,
                                    const ash::ShelfItem* item) override;
   GPUSupport* CreateGPUSupport() override;
   base::string16 GetProductName() const override;
   gfx::Image GetDeprecatedAcceleratorImage() const override;
 
  private:
+  std::unique_ptr<app_list::AppListShower> app_list_shower_;
+
   DISALLOW_COPY_AND_ASSIGN(ShellDelegateMus);
 };
 
 }  // namespace sysui
 }  // namespace ash
 
 #endif  // ASH_MUS_SHELL_DELEGATE_MUS_H_