Accept CSS url()s without quotes.

Accept CSS url()s without quotes.

This inlines images in the CSS url() function, even if the image name
is not surrounded by quotes.  e.g. url(test.png) is now treated like
url('test.png').  The Google CSS style guide recommends using url()
without quotes, and this allows us to follow that style.

BUG=https://code.google.com/p/chromium/issues/detail?id=138849

Committed: https://code.google.com/p/grit-i18n/source/detail?r=62

[newt (away), 2012-07-24 23:41:54]

I think this is a desirable change.  Let me know what you think.  Thanks.

[newt (away), 2012-07-25 21:03:24]

Here's the complete change, test and all.  (I probably should have mentioned
that the previous patch was a hastily uploaded draft to make sure I was on the
right track.)

[Jói, 2012-07-25 21:45:22]

LGTM, great, thanks!