UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/70.0.3538.102 Safari/537.36

Steps to reproduce the problem:
I have an object (call it 'foo') that contains another object (call it 'bar'), where bar is an instance of the simple Three.js EventDispatcher class (https://github.com/mrdoob/three.js/blob/dev/src/core/EventDispatcher.js).

The `foo` object creates a function (call it `handler`) and passes it to `bar` by calling `bar.addEventListener('some-name', handler)` and at that point `handler` gets stored inside of the `EventDispatcher#_listeners` property of `bar`.

When there are no references to both `foo` and `bar`, and I have not called `bar.removeEventListener('some-name', handler)` to remove the handler, both `foo` and `bar` remain in memory and are not garbage collected, although they are unreachable!

What is the expected behavior?
I expected `foo` and `bar` to both be collected.

What went wrong?
But apparently they will not be collected.

Did this work before? N/A 

Chrome version: 70.0.3538.102  Channel: n/a
OS Version: OS X 10.14.1
Flash Version: 

If I do change my code to call `bar.removeEventListener('some-name', handler)`, then both `foo` and `bar` will be collected.

My expectation is that although `foo` and `bar` are linked together because the handler contained by `foo` is held inside of `bar`, that they both (and the handler) should be collected.

I'd love to make an reproduction, but I'm overloaded with my daily job and personal stuff and the code base I'm working is private and large.

More details in the following Three.js GitHub issue: https://github.com/mrdoob/three.js/pull/15292