chromium: Update all channels to latest versions.

Version 29 has now made it into stable, the release announcement blog
post can be found here:

http://googlechromereleases.blogspot.de/2013/08/stable-channel-update.html



Overview of the updated channels:

stable: 28.0.1500.95 -> 29.0.1547.57
beta:   29.0.1547.49 -> 29.0.1547.57
dev:    30.0.1588.0  -> 30.0.1599.10 (userns patch updated)

All channels build fine and are tested (manually at the moment, until we
can run the test suite).

The userns patch for version 30.0.1599.0 from the dev channel didn't
apply anymore and is now rebased against 30.0.1599.10.

In addition, in version 30 the gyp flag for setting the sandbox path
isn't recognized anymore, so we patch it into the source directly.

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