Java Plugin for Chrome on OS X Mountain Lion 10.8.2
You are in luck, Apple released a "fix" for this issue:
http://support.apple.com/kb/HT5559
Basically Apple has provided some terminal commands that move the plug-in from the disabled folder to where it needs to be to work in Chrome.
However you would be better off (read: SAFER!) by using the updated Java plugin from Oracle and a browser that can use that plugin, like Firefox or Safari.
The Chromium project is working on it according to issue 18323, 115774 and 175129. So just give issue 18323 and issue 115774 a star to raise its importance for the Chromium developers.