Chrome: 50.0.2661.67 beta-channel
OS: ChromeOS (observed on minnie, clapper, link)
Did not verify on other platforms.

Steps to reproduce:
1. Open a browser window with the bookmarks bar showing.
2. Wait ~4 seconds.
3. Close the window.

What happens:
Sometimes the entire bookmarks bar will abruptly disappear (buttons as well as background) before the window-closing animation has completed.

What should happen instead:
The bookmarks bar should disappear gradually as part of the window-closing animation.


Other observations:

* It seems much easier to see this on an actual device than on a local build.

* This will also reproduce with --top-chrome-md=non-material, but not as frequently. It also doesn't look as bad; most frequently only the buttons disappear but not the bookmarks bar background.

* This reproduces in 44.0.2398.3 dev-channel, before any MD work landed. Similar to the above point, this does not look as bad as it does with MD enabled.

The evidence seems to suggest that this is a long-standing polish issue that has been made worse by recent MD-related changes to the bookmarks bar (re-ordering of layers, ripple/hover animations, clipping rules, etc.)