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>
chromium: Update dev channel to v30.0.1568.0.

The sha256 has changed upstream for 30.0.1566.2 and in addition there is
a new version available, so let's switch to the new version.

Unfortunately the user namespaces sandbox patch doesn't apply anymore
because of http://crbug.com/242290, so this adds a rebased version on
top of the current trunk of Chromium.

In order to build version 30, file is now needed as an additional build
input, because it is used by gyp.

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