chromium/content/test/data/accessibility/html/form-validation-message-expected-mac.txt

AXWebArea
++AXGroup AXSubrole=AXApplicationAlert AXDescription='Please enter pet name'
++AXGroup
++++AXGroup
++++++AXStaticText AXValue='Pet name:'
++++AXTextField AXErrorMessageElements=[:2] AXTitle='Pet name:'