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chromium/content/test/data/accessibility/aria/aria-live-with-content-expected-mac.txt 

AXWebArea
++AXGroup AXSubrole=AXApplicationMarquee AXARIALive='off'
++++AXStaticText AXValue='Off'
++AXGroup AXSubrole=AXApplicationMarquee AXARIALive='polite'
++++AXStaticText AXValue='Polite'
++AXGroup AXSubrole=AXApplicationMarquee AXARIALive='assertive'
++++AXStaticText AXValue='Assertive'