Add VectorIconButton functionality to ImageButton.

ui/views/view.cc

Index: ui/views/view.cc
diff --git a/ui/views/view.cc b/ui/views/view.cc
index 359ef565fd88ae041f2769b70f6fc87f3360237d..e0e0917768cf2f511bacf67823b91812e6c93b5c 100644
--- a/ui/views/view.cc
+++ b/ui/views/view.cc
@@ -2035,6 +2035,8 @@ void View::PropagateNativeThemeChanged(const ui::NativeTheme* theme) {
     for (auto* child : children_)
       child->PropagateNativeThemeChanged(theme);
   }
+  for (ViewObserver& observer : observers_)
+    observer.OnNativeThemeChanged(this, theme);
   OnNativeThemeChanged(theme);
 }
 
@@ -2501,6 +2503,8 @@ void View::PropagateThemeChanged() {
     for (auto* child : base::Reversed(children_))
       child->PropagateThemeChanged();
   }
+  for (ViewObserver& observer : observers_)
+    observer.OnThemeChanged(this);
   OnThemeChanged();
 }