Commented Issue: When the phonetextbox is focused, do not switch to hint mode when text is empty [10192]

repro:

try text in phone text box,
delete all text,
switches back to hint mode,
type again -> uses the wrong brush!
Comments: ** Comment from web user: shawnoster **

If you want to make it match Metro exactly then instead of modifying UpdateHintVisibilty update OnTextChanged() to not call UpdateHintVisibilty. At no point when the PhoneTextBox has focus should you see the hint.