[GTK] accessibility/secure-textfield-title-ui.html is failing

[GTK] accessibility/secure-textfield-title-ui.html is failing
https://bugs.webkit.org/show_bug.cgi?id=98375

Reviewed by Chris Fleizach.

Modify the test to check the childrenCount of the titleUIElement in order
to determine where the element text is exposed. On the Mac, it's exposed
in StaticText children; in ATK, in the element itself. The test was failing
because it assumed the text was in the first child of the element.

* accessibility/secure-textfield-title-ui.html: Modified.
* platform/gtk/TestExpectations: Unskipped the failing test.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@183684 268f45cc-cd09-0410-ab3c-d52691b4dbfc