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chromium/content/test/data/accessibility/mac/attributed-string/mark.html 

<!--
@SCRIPT:
  tr_mark:= mark.AXTextMarkerRangeForUIElement(mark)
  mark.accessibilityAttributeValue(AXAttributedStringForTextMarkerRange, tr_mark)
-->
<!DOCTYPE html>
<div role="mark" id="mark">Mark Text</div>