Created attachment 63799 [details]
Reduced test case that reproduces the bug
A script on the local filesystem (i.e., a file:// URL) that's loaded via a script node added after the window.onload event has fired will never be reloaded until the cache is manually cleared. In Google Chrome (which also exhibits this bug), even manually clearing the cache is ineffective.
When the same script is injected before the window.onload event has fired, it behaves as expected and is reloaded normally whenever the page is refreshed.
1. Download the attached test.zip file and extract it.
2. Open the extracted test.html file from your local filesystem. You should see the string "foo" in bold at the bottom of the page.
3. Edit test.js and change the value of the string to "bar".
4. Reload the page. You'll still see "foo".
5. (If using Google Chrome) Clear your cache. Reload. Still "foo".
*** This bug has been marked as a duplicate of bug 30862 ***