chromium: Minimal build (no install) from source.

This only gets chromium to build so far, installation is missing by upstream, so
we need to manually copy the corresponding files. And I guess with nix, we also
need to patch a few paths on installation.

Another issue is that at the moment, a lot of dependencies are used from the
source tree, rather than from the system.

Also, it would be nice to build using LLVM, as it really speeds up compilation a
*LOT* and also has the side effect of resulting in smaller binaries.

Working unit tests would be nice, too. Unfortunately they're quite heavyweight
and take hours to run, so I guess "someday" would be the most appropriate time
to integrate.

Further todo's:

- Allow to disable GConf, GIO and CUPS.
- Option to disable the sandbox (for whatever reason the user might have).
- Integrate gold binutils.
- Pulseaudio support.
- Clearly separate Linux specific stuff.
chromium: Add an install phase.

This tries to put pathes unte the same directory as the previous prebuilt
version of Chromium.
chromium: Add an update script.

It fetches the latest version based on the bucketlist XML from
commondatastorage and generates a "source.nix" which contains an attribute set
about where to fetch the latest version.

The XML is parsed in a somewhat hackish way using sed, but as this is just an
updater, its okay and we don't want to break a fly on the wheel by employing a
full XML parser.
chromium: Generate the latest source.nix.
chromium: Clean up build flags.

This also includes setting compiler architectures and paths.
chromium: Enable seccomp by default.

If useSELinux is not set, enable seccomp mode by default and avoid building the
SUID helper sandbox at all. This involves a small patch which causes the
commandline arguments to be swapped: --disable-seccomp-sandbox to disable it,
while the option is active by default.
chromium: Add "which" to build dependencies.

This is needed by a lot of scripts within chromium, so we're not going to patch
them using type, which is shell-specific anyway.
chromium: Use system libraries whenever possible.

There are still some libraries left, which we either need to patch or provide
more recent versions. Plus we're going to use openssl, as libnss doesn't want to
do proper SSL (let's debug this later).
chromium: Rename "chrome" binary to "chromium".

This is to make it more consistent with the naming of the package file and also
consistent with the build, as we're not using the Google branded version.

In addition the derivation attribute set now has a packageName value which can
be used to easily switch the binary names and paths, just in case we want to
switch to using "chrome" (or something entirely different) again.
chromium: Use patches from system OpenSSL.

This is mainly because of the patch to use OPENSSL_X509_CERT_FILE as a way to
specify the CA bundle. A browser which isn't able to verify SSL certificates
might be somewhat useless.
chromium: Allow to switch off openssl support.

Currently building fails with NSS, so we're using OpenSSL by default. And that's
why we want to make this configurable so if we manage to fix that build failure,
we could switch to using NSS by default.
chromium: Add flag to disable Gnome support.

This also separates gcrypt and gconf from the basic dependencies.
Unfortunately we cannot get rid of dbus_glib altogether, but maybe we want to
work on a patch to get rid of it? On the other hand it seems to be a TODO of the
chromium project itself, so let's wait and see.
chromium: Add mesa to build dependencies.

This finally enables support for WebGL and accelerated rendering.
chromium: Update source to version 21.0.1179.1.
chromium: Implement handling of enableCUPS.

We also need to patch the compilation process, so it allows deprecated
declarations when building support for the cups backend. In addition, we also
need to add libgcrypt to dependencies as it's needed by the cups implementation.
chromium: Enable proprietary codecs by default.

We now switch to using bundled ffmpeg, as this adds stuff such as support for
the H.264 codec.
chromium: Add dependency for libselinux.

This doesn't really work at the current state of NixOS and SELinux support, but
will make it easier in case we someday support SELinux altogether.
chromium: Cleanup dependencies.

This mostly is a code structure change, but also involves deleting some unused
dependencies and adding a few constraints on existing ones.
chromium: Use bundled versions of some libraries.

These libraries are heavily patched by the chromium project itself, so let's use
the bundled versions as those won't build anyway and also don't break functional
purity.
chromium: Simplify names of getConfig options.

This makes it easier to remember, as so far the naming wasn't quite consistent,
sometimes "use*", sometimes "enable*". So in using just use the feature name
itself, it should be pretty clear.