Er, are you sure? I just tried this with Facebook and what you describe did not happen.
The access control tab in the keychain entry had Safari as the only listed application. When I then visited the site in Chrome, it asked for permission to access the keychain. When I clicked "Allow" it worked, but Chrome was not added to the "Always allow access by these applications" list and re-prompted when I refreshed the page. When I then clicked on "Always Allow", it added Chrome to the application access list, and I'm no longer prompted for access to the keychain.
At no point was an additional entry added to the keychain.
I did notice that when Safari offered to remember the password, with an additional option to make it so that only Safari could access that password. Is it possible that you clicked on that and Chrome had to create a new entry?
Edit: I tried getting that option again to test setting it, deleting the facebook entry in the keychain and then logging in again in Safari. It no longer asks me if I want only Safari to have access to that...not sure why it won't.
Let me rephrase: on a default, clean Chrome install on 10.8.4, you are wrong. If you can't find some exculpatory evidence, I'm going to assume user error, perhaps in how you have your keychain set up.
Meanwhile I see no bug on https://code.google.com/p/chromium/issues/list filed today on the topic, and you obviously don't use Chrome as your primary browser, so I'm not going to worry about you. Cheers.
What possible Keychain setting could make Chrome copy a users password into a new keychain item, with a DIFFERENT NAME and give itself full access?
I can just as easily claim you have a weird keychain/chrome setting: no one else has disputed my claim about what it does, others have even acknowledged seeing the same behaviour.
The access control tab in the keychain entry had Safari as the only listed application. When I then visited the site in Chrome, it asked for permission to access the keychain. When I clicked "Allow" it worked, but Chrome was not added to the "Always allow access by these applications" list and re-prompted when I refreshed the page. When I then clicked on "Always Allow", it added Chrome to the application access list, and I'm no longer prompted for access to the keychain.
At no point was an additional entry added to the keychain.
I did notice that when Safari offered to remember the password, with an additional option to make it so that only Safari could access that password. Is it possible that you clicked on that and Chrome had to create a new entry?
Edit: I tried getting that option again to test setting it, deleting the facebook entry in the keychain and then logging in again in Safari. It no longer asks me if I want only Safari to have access to that...not sure why it won't.