Add ash devtools client

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_