[GTK][WTR] Implement AccessibilityUIElement::stringValue
https://bugs.webkit.org/show_bug.cgi?id=102951

Reviewed by Martin Robinson.

Implement AccessibilityUIElement::stringValue in the ATK backend
in the same manner it is implemented in DumpRenderTree.

* WebKitTestRunner/InjectedBundle/atk/AccessibilityUIElementAtk.cpp:
(WTR::replaceCharactersForResults):
(WTR):
(WTR::AccessibilityUIElement::stringValue):


git-svn-id: svn://svn.chromium.org/blink/trunk@135485 bbb929c8-8fbe-4397-9dbb-9b2b20218538
int AccessibilityUIElement::lineForIndex(int index)
{
    return 0;
}

int AccessibilityUIElement::lineForIndex(int index)
{
    return 0;
}
