Do not wrap text in the flakiness dashboard revision popup

Text wrapping is a little funny in an absolute-positioned element: the
available width of an off-screen element is zero which causes wrapping.
I created a minimal example of this is at http://pr.gg/wrapgenius.html
This behavior is well-known and there are workarounds [1].

The flakiness dashboard popup is similarly affected (see:
http://pr.gg/flakywrapping.png). Because the flakiness dashboard
revision popup has breaks already, we can just use
white-space: nowrap to fix this without any involved workarounds.

[1] http://stackoverflow.com/questions/14819574/preserve-normal-word-wrapping-inside-absolutely-positioned-container

NOTRY=true

Review URL: https://codereview.chromium.org/403553002

git-svn-id: svn://svn.chromium.org/blink/trunk@178519 bbb929c8-8fbe-4397-9dbb-9b2b20218538