User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/44.0.2403.130 Safari/537.36 Steps to reproduce: 1. Open http://digitalfeed.net/firefox_issue_3.html in Firefox 2. Right-click in the IFrame and choose Inspect Element 3. Choose the 'Debugger' tab in the dev tools 4. Select firefox_issue_3_inner.js in debugger (this file is included inside the IFrame) 5. Press 'Stop blackboxing this source' 6. Press the 'Pretty print' button 7. Set a breakpoint in the pretty-printed source 8. Refresh the browser window 9. Watch as the debugger hits a non-existent breakpoint in firefox_issue_3_outer.js (which is in the outer page) Actual results: The debugger acted as if the breakpoint was in the file in the page outside the IFrame, rather than in the JS file inside the IFrame Note: if you put the breakpoint in the IFrame and then right-click refresh the IFrame, the browser will crash: see Bug 1191191 Expected results: The debugger should have paused on the breakpoint in firefox_issue_3_inner.js inside the IFrame.

Also reproduced on FF39 on Win7.