Apple - How to tell Google Chrome to use my Keychain

Since v. 45 of chrome passwords are not synced to the OSX keychain anymore, the support has been dropped completely.

https://code.google.com/p/chromium/issues/detail?id=466638

Remove OS X Keychain integration for saved passwords

Starting in OS X 10.9, Apple introduced the iCloud Keychain. This manifests itself as the “Local Items” keychain in Keychain Access. Items in this keychain are only accessible to applications with the keychain-access-groups entitlement [1][2]. This, like other iCloud entitlements, is “available only to apps submitted to the App Store or to the Mac App Store” [3].

The effect of this is that on 10.9 and 10.10, passwords stored in Safari are not accessible to Chrome (but passwords originated in Chrome are still shared to Safari)

Later in the doc:

All the changes hit the 45 release. The plan is to get rid of the complicated Keychain code, thereby improving the robustness of the Chrome Password manager.

This answer is no longer correct: OS X Keychain support is being removed from Chrome 45. See @patte8's answer for more information.

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As far as I can tell, Chrome uses the keychain automatically:

Google Chrome can save your usernames and passwords for different websites. The browser can then automatically complete the sign-in fields for you when you next visit these websites.

These passwords are stored in the same system that contains your saved passwords from other browsers. On a Mac, Google Chrome uses the Keychain Access to store your login information.

Source: https://support.google.com/chrome/bin/answer.py?hl=en&answer=95606

(I'll leave the bit about choosing a specific keychain for Chrome to someone else, I don't know if that can be done)