If you put the Library in the Overflow menu and then select library -> bookmarks (with a very lage bookmarks list) it breaks the overflow menu. The menu hangs for a while, flashes, and disappears. Steps to reproduce: 1. Menu -> Customization 2. Add Library to the overflow menu 3. Click overflow menu -> library -> bookmarks Results: menu breaks Expected results: menu works. Tested on WIn7 and Win10 nightly builds with large number of bookmarks. Works fine if you have a new profile with just a few bookmarks but fails with a large number of bookmarks.

OK. It doesn't completely fail; it just takes a long time to show the bookmarks and part of the menu disappears while it's waiting. Some of the time it causes the content area to repaint.

The library -> bookmarks transition is much faster less janky in the hamburger menu.

Here's a video of it with the very long pause after clicking Bookmarks before the menu is briefly truncated and then restored with bookmarks. https://youtu.be/ziaW1ZexLO0

History does the same thing as Bookmarks. It hangs the menu for many seconds before filling in.