Typing in URL bar causes website reflow flashing

[canadaduane]

When visiting a site such as https://code.thumby.us/, if I type something into the URL bar (e.g. "t") the website flashes for a moment as the autosuggest options push the website content down. It's particularly visible in complex rendering such as the "code blocks" area of the example site mentioned above:

It looks like there are at least 2 "frames" in the reflow flash, such that the 1st frame renders the website's new location with code blocks not quite fully rendered, then the 2nd frame renders with the code blocks fully rendered.