The toolbar is white in an undocked inspector.
Looks like I broke this in r61215.
Created attachment 58912 [details] Speculative Fix Not a real patch (missing a ChangeLog). But this removes the "transparent" and replaces it with a real gradient. It then makes sure the inactive gradient takes over when .inactive comes into play (it may need more specificity).
Created attachment 58914 [details] Patch
Collision! Like mitz warned in IRC, this could be affecting other pages, or widgets that used to rely on this behavior. But you're right its unspecified behavior to rely on and I'd have expected it to be white.
http://trac.webkit.org/changeset/61274