URL: https://mixer.com/csharpfritz

Browser / Version: Firefox 59.0
Operating System: Windows 10
Tested Another Browser: Unknown

Problem type: Design is broken
Description: After opening then closing the Account panel (top-right blue-ish icon), the page doesn't reflow correctly.
Steps to Reproduce:

layout.css.servo.enabled: true

1. Open account panel
2. Close account panel
   

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