The default configuration of the tool detects goog.Disposable objects which were not dispose()d. goog.EventTarget is a subclass of goog.Disposable, and if an EventTarget is not disposed, event listeners are not discarded properly, and event listeners in turn keep DOM objects alive. It's possible to configure the tool to detect other similar misuses.
You can find more details about this project here.
If Internet Explorer is brave enough to ask you to be your default browser, you're brave enough to ask that girl out. Do we have to be so cruel to IE?