 public class ButtonBase extends SkinnableComponent implements IFocusManagerComponent
 {
     include "../../core/Version.as";
+    
+    //--------------------------------------------------------------------------
+    //
+    //  Class mixins
+    //
+    //--------------------------------------------------------------------------
+
+    /**
+     *  @private
+     *  Placeholder for mixin by ButtonAccImpl.
+     */
+    mx_internal static var createAccessibilityImplementation:Function;
 
     //--------------------------------------------------------------------------
     //

    //  Overridden properties: UIComponent
    //
    //--------------------------------------------------------------------------

    //----------------------------------
    //  baselinePosition
    //----------------------------------

[DefaultTriggerEvent("click")]

[DefaultProperty("label")]

[AccessibilityClass(implementation="spark.accessibility.ButtonAccImpl")]

/**
 *  The ButtonBase component is the base class for the all Spark button components.
