chromium/content/test/data/accessibility/mac/attributes/ax-help-expected.txt

link.accessibilityAttributeNames.has(AXHelp)='yes'
link.accessibilityAttributeValue(AXHelp)='help description'
not_applicable.accessibilityAttributeNames.has(AXHelp)='yes'
not_applicable.accessibilityAttributeValue(AXHelp)=NULL