Create a unified UIElement interface for Widget, View and Window.

ash/devtools/ui_element_delegate.h

Index: ash/devtools/ui_element_delegate.h
diff --git a/ash/devtools/ui_element_delegate.h b/ash/devtools/ui_element_delegate.h
new file mode 100644
index 0000000000000000000000000000000000000000..841ebeaa3d1865e65f91c35c3f0c81b9ee975bdb
--- /dev/null
+++ b/ash/devtools/ui_element_delegate.h
@@ -0,0 +1,35 @@
+// Copyright 2017 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_UI_ELEMENT_DELEGATE_H_
+#define ASH_COMMON_DEVTOOLS_UI_ELEMENT_DELEGATE_H_
+
+#include <vector>
+
+#include "ash/ash_export.h"
+#include "base/macros.h"
+
+namespace ash {
+namespace devtools {
+
+class UIElement;
+
+class ASH_EXPORT UIElementDelegate {
+ public:
+  UIElementDelegate(){};
+  ~UIElementDelegate(){};
+  virtual void OnUIElementAdded(
+      int node_id,
+      UIElement* child_ui_element,
+      std::vector<UIElement*>::iterator prev_siblings);
+  virtual std::vector<UIElement*>::iterator OnUIElementRemoved(int node_id);
+  virtual void OnUIElementBoundsChanged(int node_id);
+
+  DISALLOW_COPY_AND_ASSIGN(UIElementDelegate);
+};
+
+}  // namespace devtools
+}  // namespace ash
+
+#endif  // ASH_COMMON_DEVTOOLS_UI_ELEMENT_DELEGATE_H_