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

ash/common/devtools/ui_element_delegate.cc

+
+// For WindowElement observers
+void UIElementDelegate::NotifyOnWindowHierarchyChanging(
+    const aura::WindowObserver::HierarchyChangeParams& params) {
+  OnWindowHierarchyChanging(params);
+}
+
+void UIElementDelegate::NotifyOnWindowHierarchyChanged(
+    const aura::WindowObserver::HierarchyChangeParams& params) {
+  OnWindowHierarchyChanged(params);
+}
+
+void UIElementDelegate::NotifyRemoveWindowTree(WmWindow* window,
+                                               bool remove_observer) {
+  RemoveWindowTree(window, remove_observer);
+}
+
+void UIElementDelegate::NotifyAddWindowTree(WmWindow* window) {
+  AddWindowTree(window);
+}
+
+void UIElementDelegate::NotfiyOnWindowBoundsChanged(WmWindow* window) {
+  for (auto& observer : observers_)
+    observer.OnWindowBoundsChanged(window);
+}
+
+// For ViewElement observers
+void UIElementDelegate::NotifyRemoveViewTree(views::View* view,
+                                             views::View* parent,
+                                             bool remove_observer) {
+  RemoveViewTree(view, parent, true);
+}
+
+void UIElementDelegate::NotifyAddViewTree(views::View* view) {
+  AddViewTree(view);
+}
+
+void UIElementDelegate::NotifyOnViewBoundsChanged(views::View* view) {
+  for (auto& observer : observers_)
+    observer.OnViewBoundsChanged(view);
+}
+
+// For WidgetElement observers
+void UIElementDelegate::NotifyOnWidgetBoundsChanged(views::Widget* widget) {
+  for (auto& observer : observers_)
+    observer.OnWidgetBoundsChanged(widget);
+}