Theme-install preview toolbars don't consistently load

[melchoyce]

The "add theme" preview toolbar doesn't consistently load for me. See it in action: ​https://cloudup.com/cHSv7TS9dPz

Not seeing anything in the console.

[celloexpressions]

Most likely a browser rendering issue, but something we may be able to fix. I can't reproduce in Chome 36 or Firefox 31 on Windows 8.1, even with navigating in and out of the previewer very quickly with the keyboard.

There's a good chance this was introduced in 4.0 with the changes from buttons to icons here; @melchoyce, can you try it on other browsers and in 3.9 and narrow down where the issue is? If it isn't a regression, we need to punt it.

[adamsilverstein]

Mel, I tried to reproduce the issue mentioned in this ticket without luck - although your screen-cast makes it look easy.

I tried in Chrome/Dev and Firefox. Any tricks to getting the bug to surface? what browser are you using?

[helen]

Punting for now, this may very well be a "worksforme" situation even though I know it's been happening to melchoyce for a while now.

[ocean90]

Seeing this now too in Chrome 37/OSX, see ​https://cloudup.com/iEQan6lsivD.

[ocean90]

With 28898.patch​ I see the header and footer again. But no idea what's going on here.

[ocean90]

Seems like an issue in combination with a Retina screen. On a Retina screen it's hidden, after moving the browser to the my second screen (non-Retina) header and footer are coming back.

[adamsilverstein]

verified the patch fixes the problem. i think removing overflow: auto; makes sense, not sure why its there. I didn't see any adverse side effects from the change and after the patch can no longer reproduce the issue.

looks good, nice catch!

[markjaquith]

In 30101:

Fix weird HiDPI screen rendering issue with theme install preview toolbar

fixes #28898
props ocean90