When I have the Google Developer tools open, I noticed that clicking "Test Me" on http://panopticlick.eff.org/ doesn't fully load until I close the tools. Of course I can reopen the tools later once the page fully loads, but I want to understand why the blocking operation is occuring.
Why must I close the dev tools? Is this a bug?
It could be that your DevTools are configured to pause on exceptions that occur in the inspected page. Switch to the Scripts panel and click the octagonal icon with the "pause" symbol in the bottom left corner until it becomes black, with "don't pause on exceptions" as a tooltip -- then try again.