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 a67ae7f942901f34ae79b0ddc871ab9d6b9b460e..ac0161a2b7d067942fa2dc24eb4b91ee5c66ff70 100644
--- a/ui/views/view.cc
+++ b/ui/views/view.cc
@@ -2038,6 +2038,8 @@ void View::PropagateNativeThemeChanged(const ui::NativeTheme* theme) {
     for (auto* child : children_)
       child->PropagateNativeThemeChanged(theme);
   }
+  for (ViewObserver& observer : observers_)
+    observer.OnNativeThemeChanged(this, theme);
   OnNativeThemeChanged(theme);
 }
 
@@ -2504,6 +2506,8 @@ void View::PropagateThemeChanged() {
     for (auto* child : base::Reversed(children_))
       child->PropagateThemeChanged();
   }
+  for (ViewObserver& observer : observers_)
+    observer.OnThemeChanged(this);
   OnThemeChanged();
 }