chromium: Revert back to copying bundled sources.

I'm giving up on this after several attempts to correctly unbundle the
largest part, namely Google's WebKit fork Blink. Right now it's so much
tied into the Chromium source it's going to be fairly hard to do if
you're not working full time on it.

Also, the intermediate steps needed to do this properly would introduce
uneccesary complexity on our side, so we really need to finish this
without leaving it in the "messy" state in order to not make Chromium
even more difficult to maintain than it is already.

However, anyone who wants to proceed on this messy step is free to
revert this commit and continue doing so. In my case I'm going to try
again once https://crbug.com/239107 and https://crbug.com/239181 are
fixed in _stable_ (I don't want to introduce *lots* of conditionals on
the version either).

Signed-off-by: aszlig <aszlig@redmoonstudios.org>