assignment of mx_internal property should fail when done via mxml

Steps to reproduce:
1. Compile the attached test case using mxmlc

Actual Results:
Compiles without error

Expected Results:
Should give error for dragScrollInitialDelay (defined in mx_internal namespace in LayoutBase.as)

in <s:TileLayout id="tileLayout" columnWidth="50" requestedColumnCount="4"
horizontalGap="2" verticalGap="2" orientation="columns" dragScrollInitialDelay ="0"/>