Add ViewObserver to View for view updates

ui/views/view.cc

Index: ui/views/view.cc
diff --git a/ui/views/view.cc b/ui/views/view.cc
index b6cd9d0e97f9345128f754a62f0b80e15fa2430f..92223157d4c8671aaa2c55aab4c006d1ee25b265 100644
--- a/ui/views/view.cc
+++ b/ui/views/view.cc
@@ -51,6 +51,7 @@
 #include "ui/views/drag_controller.h"
 #include "ui/views/focus/view_storage.h"
 #include "ui/views/layout/layout_manager.h"
+#include "ui/views/view_observer.h"
 #include "ui/views/views_delegate.h"
 #include "ui/views/widget/native_widget_private.h"
 #include "ui/views/widget/root_view.h"
@@ -220,6 +221,9 @@ void View::AddChildViewAt(View* view, int index) {
 
   if (layout_manager_.get())
     layout_manager_->ViewAdded(this, view);
+
+  for (ViewObserver& observer : observers_)
+    observer.OnChildViewAdded(view);
 }
 
 void View::ReorderChildView(View* view, int index) {
@@ -247,6 +251,9 @@ void View::ReorderChildView(View* view, int index) {
   InitFocusSiblings(view, index);
   children_.insert(children_.begin() + index, view);
 
+  for (ViewObserver& observer : observers_)
+    observer.OnChildViewReordered(view);
+
   ReorderLayers();
 }
 
@@ -298,6 +305,9 @@ void View::SetBoundsRect(const gfx::Rect& bounds) {
   gfx::Rect prev = bounds_;
   bounds_ = bounds;
   BoundsChanged(prev);
+
+  for (ViewObserver& observer : observers_)
+    observer.OnViewBoundsChanged(this);
 }
 
 void View::SetSize(const gfx::Size& size) {
@@ -418,6 +428,9 @@ void View::SetVisible(bool visible) {
       parent_->NotifyAccessibilityEvent(ui::AX_EVENT_CHILDREN_CHANGED, false);
     }
 
+    for (ViewObserver& observer : observers_)
+      observer.OnViewVisibilityChanged(this);
+
     // This notifies all sub-views recursively.
     PropagateVisibilityNotifications(this, visible_);
     UpdateLayerVisibility();
@@ -436,7 +449,11 @@ void View::SetEnabled(bool enabled) {
   if (enabled != enabled_) {
     enabled_ = enabled;
     AdvanceFocusIfNecessary();
+
     OnEnabledChanged();
+
+    for (ViewObserver& observer : observers_)
+      observer.OnViewEnabledChanged(this);
   }
 }
 
@@ -1364,6 +1381,19 @@ int View::GetLineScrollIncrement(ScrollView* scroll_view,
   return 0;
 }
 
+void View::AddObserver(ViewObserver* observer) {
+  CHECK(observer);
+  observers_.AddObserver(observer);
+}
+
+void View::RemoveObserver(ViewObserver* observer) {
+  observers_.RemoveObserver(observer);
+}
+
+bool View::HasObserver(const ViewObserver* observer) const {
+  return observers_.HasObserver(observer);
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // View, protected:
 
@@ -1839,6 +1869,9 @@ void View::DoRemoveChildView(View* view,
 
   if (layout_manager_)
     layout_manager_->ViewRemoved(this, view);
+
+  for (ViewObserver& observer : observers_)
+    observer.OnChildViewRemoved(view, this);
 }
 
 void View::PropagateRemoveNotifications(View* old_parent, View* new_parent) {