UserAgent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/55.0.2883.87 Safari/537.36

Steps to reproduce the problem:
1. Turn on chrome://flags/#enable-add-to-shelf
2. Visit a localhost site (served over http) - extremely common in development
3. Look in the console for the error message "Site cannot be installed: the page is not served from a secure origin"
4. Navigate to https://stackoverflow.com/questions/41863050/why-does-chrome-keep-displaying-site-cannot-be-installed-the-page-is-not-serve/
5. Look in the console for the error message "Site cannot be installed: the page has no manifest <link> URL"
6. Go to an HTTPS site you've never visited before, such as https://www.random.org/integers/ and notice the same complain about the manifest.

What is the expected behavior?
No error messages, and certainly no messages on the first visit to a site, before the A2HS heuristics have been met.

What went wrong?
Site cannot be installed: the page is not served from a secure origin

Site cannot be installed: the page has no manifest <link> URL

Did this work before? N/A 

Chrome version: 55.0.2883.87  Channel: stable
OS Version: 
Flash Version: 

The vast majority of sites don't have a manifests, so it makes little sense to display those error messages on any random web site. On the other hand, they should be displayed when the developer is specifically working on A2HS functionality, and there should be mechanisms for allowing the error on demand, or suppressing further displays of the error.