Form defaultButton doesnt work when using Spark ToggleButton

Found in 10030

Steps to reproduce:
1. Compile and run attached .MXML file.
2. Click in each of the Spark/Halo TextInput controls and observe if default button is highlighted/emphasized.
3. Press Enter while each TextInput has focus and observe when/if the defaultButton is triggered.

Actual Results:
Halo Form + Spark ToggleButton as defaultButton == FAIL
Halo Form + Spark Button as defaultButton = pass
Halo Form + Halo toggle Button as defaultButton = pass
Halo Form + Halo Button as defaultButton = pass

Expected Results:
Halo Form + Spark ToggleButton as defaultButton should work and trigger the defaultButton's click handler.

Workaround (if any):
INstead of Spark ToggleButton use a Spark Button or Halo Button/toggle Button.