Fix bug where removed (but not deleted) windows are not reflected in the tree properly

ash/common/devtools/ash_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_ASH_DEVTOOLS_DOM_AGENT_H_
 #define ASH_COMMON_DEVTOOLS_ASH_DEVTOOLS_DOM_AGENT_H_
 
 #include "ash/common/wm_shell.h"
 #include "ash/common/wm_window_observer.h"
 #include "base/compiler_specific.h"
@@ skipping 10 matching lines @@
  public:
   explicit AshDevToolsDOMAgent(ash::WmShell* shell);
   ~AshDevToolsDOMAgent() override;
 
   // DOM::Backend
   ui::devtools::protocol::Response disable() override;
   ui::devtools::protocol::Response getDocument(
       std::unique_ptr<ui::devtools::protocol::DOM::Node>* out_root) override;
 
   // WindowObserver
-  void OnWindowDestroying(WmWindow* window) override;
+  void OnWindowTreeChanging(WmWindow* window,
+                            const TreeChangeParams& params) override;
   void OnWindowTreeChanged(WmWindow* window,
                            const TreeChangeParams& params) override;
   void OnWindowStackingChanged(WmWindow* window) override;
 
  private:
   std::unique_ptr<ui::devtools::protocol::DOM::Node> BuildTreeForWindow(
       WmWindow* window);
   std::unique_ptr<ui::devtools::protocol::DOM::Node> BuildInitialTree();
   void AddWindowNode(WmWindow* window);
-  void RemoveWindowNode(WmWindow* window, WmWindow* old_parent);
+  void RemoveWindowNode(WmWindow* window);
   void RemoveObserverFromAllWindows();
   void AddRootWindowObservers();
   void Reset();
 
   ash::WmShell* shell_;
 
   using WindowToNodeIdMap = std::unordered_map<WmWindow*, int>;
   WindowToNodeIdMap window_to_node_id_map_;
 
   DISALLOW_COPY_AND_ASSIGN(AshDevToolsDOMAgent);
 };
 
 }  // namespace devtools
 }  // namespace ash
 
 #endif  // ASH_COMMON_DEVTOOLS_ASH_DEVTOOLS_DOM_AGENT_H_