r264037 changed the behavior of AccessibilityRenderObject::setSelectedVisiblePositionRange for the cases where the selection range is 0.

This made accessibility/textarea-selected-text-range.html to fail, returning (0,0) from selectedTextRange when the length given to setSelectedTextRange is zero.

In AccessibilityUIElementAtk.cpp's AccessibilityUIElement::setSelectedTextRange(unsigned location, unsigned length), there is this snippet which might be related:

  1888     if (!length)
     1         return atk_text_set_caret_offset(ATK_TEXT(m_element.get()), location);
     2
     3     return atk_text_set_selection(ATK_TEXT(m_element.get()), 0, location, location + length);

Link to the results history: https://results.webkit.org/?suite=layout-tests&test=accessibility%2Ftextarea-selected-text-range.html