[Mirroring] MX and Spark CheckBox check marks are inconsistently mirrored in wireframe skin when layoutDirection = rtl

Found in 4.1.0.15082

Steps to reproduce:
1. Compile and run attached MXML file with Flex 4.1+ and Wireframe (and Spark) themes.
2. Toggle between RTL and LTR.

Actual Results:
Inconsistent checkmarks in wireframe+RTL config.

Expected Results:
Consistent me!

Workaround (if any):
n/a