CONSOLE MESSAGE: line 34: Content blocker prevented frame displaying http://127.0.0.1:8000/contentextensions/block-ping.html from loading a resource from http://127.0.0.1:8000/contentextensions/resources/save-ping.php?test=contentextensions-block-ping
This test follows a link with a ping attribute where the ping URL matches a 'block' rule.  

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Frame: 'link_frame'
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Link with ping was clicked.

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Frame: 'result_frame'
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Ping not received - timed out.