Following up on @SirCharlo's comment. It seems that of the four chromium channels the only ones with a Precise Pangolin build as of this writing are the Stable and Beta ones.
So you can remove the ppa you already added as using the rm above.
sudo rm /etc/apt/sources.list.d/*chromium*
Alternately, you can use ppa-purge or the
Y PPA Manager gui, double clicking on "Remove a PPA."
Then install one of the available channel's builds. So to get the one from beta:
sudo add-apt-repository ppa:chromium-daily/beta
sudo apt-get update
sudo apt-get install chromium-browser
I guess this will do until the Precise builds are available for more bleeding edge dev/daily channels again. At least there's no "failed to fetch" error and it gets updated periodically.