Update ash to use new devtools base agent

ash/common/devtools/devtools_dom_agent.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_COMMON_DEVTOOLS_DEVTOOLS_DOM_AGENT_H_
-#define ASH_COMMON_DEVTOOLS_DEVTOOLS_DOM_AGENT_H_
-
-#include "ash/common/wm_shell.h"
-#include "components/ui_devtools/DOM.h"
-
-namespace ash {
-namespace devtools {
-
-class AshDevToolsDOMAgent : public ui::devtools::protocol::DOM::Backend {
- public:
-  explicit AshDevToolsDOMAgent(ash::WmShell* shell);
-  ~AshDevToolsDOMAgent() override;
-
- private:
-  std::unique_ptr<ui::devtools::protocol::DOM::Node> BuildInitialTree();
-
-  // DOM::Backend
-  void enable(ui::devtools::protocol::ErrorString* error) override {}
-  void disable(ui::devtools::protocol::ErrorString* error) override {}
-  void getDocument(
-      ui::devtools::protocol::ErrorString* error,
-      std::unique_ptr<ui::devtools::protocol::DOM::Node>* out_root) override;
-
-  ash::WmShell* shell_;
-
-  DISALLOW_COPY_AND_ASSIGN(AshDevToolsDOMAgent);
-};
-
-}  // namespace devtools
-}  // namespace ash
-
-#endif  // ASH_COMMON_DEVTOOLS_DEVTOOLS_DOM_AGENT_H_