Appearance Themes: #appearance needs to have a computed height

[matveb]

Since the content of #themes is all floated, #appearance ends up with no height. That throws off the scroll threshold check as it relies on the element's height. (Using overflow hidden causes other layout issues, so should be avoided.)

[matveb]

Helen suggested a helper class to deal with the clear.

[matveb]

Can we commit this one and in any case open a new ticket for dealing with a cleafix class? It's currently breaking the lazy-rendering of themes.

[helen]

I tried to get to this in my commit sprint last night, but ran out of steam. It's second on my next round, either later today or tomorrow at some point (today is a holiday in the US), after merging the theme CSS into the main admin styles. There are already some clearfixes in admin CSS - need to combine them.

[dd32]

Didn't recognise this ticket, but fixed it via [26468]

Themes: Add a clearing <br/> to the end of .theme-browser.
This is needed to cause the browser to render .theme-browser's height as it's true height, previously the reported height was 1*.theme which caused the Theme scroller to kick in immediately (as the threshold was less than 0).

[helen]

Leaving this alone at this point, but opened #26396 for the clearfix thing.