Fix selection redraw during window resize.

[gruehle]

This fixes the cosmetic problem with selection highlighting that occurs when resizing the window.

This problem is most visible in WebKit browsers.

[marijnh]

This cause another problem. If you put the cursor in the middle of a line, and then select text with shift-left, you'll see the right of the selection wobble (by a single pixel) as a result of rounding errors. I think that is a more visible problem than the one solved by this patch, so I'm not merging it as it stands.

Does the problem you were fixing occur in the demos? Or only in a different layout? In the second case, please provide some HTML that demonstrates it, since I still don't see it (in Chrome) in the demo pages.

[gruehle]

Here is a screencast that shows the issue I'm seeing. This is the Theme demo from the CodeMirror website:
http://youtu.be/UQAeGs9k73A

Other people at my office have also reproduced the problem.

Which demo file shows the single pixel wobble? I'm not seeing it on my Mac (Chrome, Firefox, Safari).

[marijnh]

Other people at my office have also reproduced the problem.

I see. I can reproduce it now, I just wasn't resizing the window
quickly enough. This is probably caused by a DOM redraw happening
before CodeMirror's resize has a chance to adjust the selection
geometry. It does always seem to go back to a consistent state when
the resizing is finished.

I don't consider this a critical issue. It'd be good to fix it, but
I'm not lying awake at night in the meantime.

Which demo file shows the single pixel wobble? I'm not seeing it on my Mac (Chrome, Firefox, Safari).

I get it in all demos on Chrome Linux. It's probably font and
drawing-engine related.