Created attachment 8472115 [details] testcase.xhtml User Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:32.0) Gecko/20100101 Firefox/32.0 (Beta/Release) Build ID: 20140801100255 Steps to reproduce: In the attachments is a testcase. Just open it and click the button to start the infinite loop. Actual results: Firefox will never ask to stop the script which causes the browser to be unresponsible until the process is closed. Expected results: The dialog to stop the script should appear after a short time.
Check your "dom.max_script_run_time" value in about:config. If set it to 2 (second), the dialog shown after a short time. Test on my Win8.1, Fx32 Beta.
A little of supplement, changing its value is to confirm whether it at works.
The value was set to 0 (I'm assuming this means that scripts are allowed to run infinite). But I'm wondering how the value got changed. The closest I can think is because I have enabled the checkbox "Don't ask me again" on the "Unresponsive script" dialog and then allowed a script to run in the past. But I was assuming that this checkbox is on a per script and per session base (or something similar) and trying to reproduce this shows that enabling the checkbox and allowing a script to run doesn't change dom.max_script_run_time. Well, who knows what changed the value so I'm marking this ticket as invalid.