goog.Disposable is an interface for disposable objects. Before dropping the last reference to an object which is an instance of goog.Disposable (or its subclass), the user code is supposed to invoke the method dispose()on the object. This method can release resources, e.g., by disposing event listeners. However, a web application might forget to call dispose() before dropping all the references to an object.
Leak finder can detect such goog.Disposable objects which were not disposed, and print out useful information (such as the stack trace when the object was created) about them. It produces machine-readable output and can be used as a part of test automation.
In order to find leaks, Leak Finder relies on goog.Disposable monitoring mode. The mode gathers all created but not yet disposed instances of goog.Disposable (and its subclasses) into an array goog.Disposable.instances_. This array will keep the objects alive. However, if an object is only kept alive by this array and other Closure data structures, it is a leak, since the user code doesn't contain any pointers to the object, and it cannot call dispose() on it.