This Firefox extension detects one very specific type of leak in chrome JavaScript and in Web pages. (Not in JavaScript components, though.) It detects when JavaScript objects in the chrome or Web page are still held by native code after the window is closed.

Some of these leaks are things that are clearly bugs in the extension (such as registering observers with the observer service forever) and some are things that arguably shouldn't leak (at varying argument strengths). The things that are exposed to Web pages are definitely things that shouldn't leak, and most of those bugs are close to being fixed. However, a bunch of those bugs are present in Firefox 1.5 and easy for extension authors to work around (call removeEventListener to match addEventListener for functions added as event listeners).