Repro steps:
1. Go to main page of youtube on chrome 66.
2. Click on the first recommended video.
3. Click on the youtube icon to go back to the main page.
4. Repeat 2-3 several times.
5. Take heap snapshot and look for EventListener.

Example retaining path:
[7] in InternalNode @2941385376
  [15] in HTMLAnchorElement @2941384608
    [31] in HTMLAnchorElement @44175
     host in system / Context @2107403
       context in handler() @2107401
          d in system / Context @1545167
            context in e() @44169
              11370 in [] @1139827
                table in WeakMap @1139825
                   109 in @1226359
                       code in _listenListeners() @305525
                            _listenListeners in HTMLElement @305283
                                Base in native_bind() @111103

The code object of _listenListeners() function retains WeakMap table.