Context menus duplication

[ChrisRaven]

Every 2 minutes the site recreates the context menus for all segments. The problem is, that the old menus aren't removed from the DOM tree. When working with a couple of hundred of segments, the number quickly raises to several thousands of DOM nodes, which leads to overall slowness of the site. Refresh helps. (all addons turned off).
To recreate, just add some segments to the website, open the Console, go to the Elements tab and wait. Every two minutes there are new "div.neuroglancer-context-menu.neuroglancer-layer-group-viewer-context-menu" nodes added with all their content, so every 2 minutes, there are 10 x number_of_segments more nodes in the tree.