chromium: Add API keys for NixOS.

As requested by some users, we finally have support for cloud sync,
spelling, geolocation and a lot more of the services that require API
keys from Google. Details about which services are involved can be found
at: http://www.chromium.org/developers/how-tos/api-keys

Thanks to Paweł Hajdan <phajdan@google.com> for giving us permission to
distribute the API keys with our build of Chromium:

> Note that the public Terms of Service do not allow distribution of the
> API keys in any form. To make this work for you, on behalf of Google
> Chrome Team I am providing you with:

> Official permission to include Google API keys in your packages and to
> distribute these packages. The remainder of the Terms of Service for
> each API applies, but at this time you are not bound by the
> requirement to only access the APIs for personal and development use,
> and Additional quota for each API in an effort to adequately support
> your users.

As noted in the source: Those keys are for use in NixOS/nixpkgs ONLY!

Signed-off-by: aszlig <aszlig@redmoonstudios.org>
chromium: Update all channels to latest versions.

So, chromium 30 entered the dev release channel, so the overview of the
current versions is:

stable: 28.0.1500.52 -> 28.0.1500.71 (builds fine, tested)
beta:   28.0.1500.52 -> 29.0.1547.22 (builds fine, tested)
dev:    29.0.1547.0  -> 30.0.1566.2  (builds fine, tested)

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