To update to the latest build of Chromium, use this bash script.

#!/bin/bash
tempfoo=`basename $0`
TMPDIR=`mktemp -q -d /tmp/${tempfoo}.XXXXXX`
if [ $? -ne 0 ]; then
	   echo "$0: Can't create temp file, exiting..."
	   exit 1
fi
LATEST=`curl http://commondatastorage.googleapis.com/chromium-browser-continuous/Mac/LAST_CHANGE`
curl -L http://commondatastorage.googleapis.com/chromium-browser-continuous/Mac/$LATEST/chrome-mac.zip -o $TMPDIR/chrome-mac.zip
unzip -qq -d $TMPDIR $TMPDIR/chrome-mac.zip
cp -R $TMPDIR/chrome-mac/Chromium.app /Applications