UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_3) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/57.0.2987.133 Safari/537.36

Steps to reproduce the problem:
1. Developer adds support for the credential management API to an application.
2. Developer cries (a little) when the feature only supports Chrome's built-in password manager.

What is the expected behavior?
Credential management API is exposed as a first class extension API.

What went wrong?
The credential management API is not accessible by extensions natively. Many users make use of third-party password managers and they all currently rely on various means of injecting JavaScript into the page to automatically fill out some element in the DOM. The credential management API brings a lot of sanity to this class of problem, and prevents plaintext creds from ever making their way into the DOM. But, unfortunately, the credential management API only accesses Chrome's built-in password store. It would be great to make it possible for extensions to register themselves as the preferred credential manager. So, when an application's own JS calls `credentials.get()`, the browser could delegate this request to an extension. 

Did this work before? No 

Does this work in other browsers? N/A

Chrome version: 57.0.2987.133 (Official Build) (64-bit)  Channel: stable
OS Version: OS X 10.12.3
Flash Version: 

This is more of a feature request. I'm not sure if this is the best "component", but I figure it is close and Mike West can move it wherever it is best to keep track of such things.