Fix race where sometimes CSS is not applied to toolstrips. I

Fix race where sometimes CSS is not applied to toolstrips. I
think this was happening because we were injecting from the the
browser at load_start, but the document might not be established
in the renderer by the time this message is received.

Since we are now not even showing the toolstrip until
load_complete, it is no big deal to delay the CSS injection
until then.

[Erik does not do reviews, 2009-04-29 22:21:43]

LGTM

great!