Mixed content error when admin is HTTPS and site is HTTP

[petenelson]

When the admin is being viewed as HTTPS but the site is HTTP, the browser is unable to access the API.

Had the same issue with my logging plugin: petenelson/wp-rest-api-log@9779f79

[johnbillion]

This is a fundamental problem with the REST API and mixed protocols. See WP-API/WP-API#259