Google is rolling out a new security panel in the DevTools section of Chrome 48 that is designed to make it easy for developers to deploy HTTPS on their websites and services.
Secure connections are a necessity today to decrease the risk of users being vulnerable to content injection (the result of that being eavesdropping, man-in-the-middle attacks, and other data modifications). What's more, HTTPS is also playing an increasingly important role in Google search algorithm, prioritizing encrypted sites with a ranking boost and in late December indicated that it has started indexing HTTPS pages by default (Google Search now crawls HTTPS equivalents of HTTP pages, even when the former are not linked to from any page).
The new security panel displays connection information for every network request in an effort to identify potential connection errors. If there is no green lock in Chrome, DevTools will provide the reason why. For example, there might be a certificate violation (which shows whether a site has proven its identity with a TLS certificate), the TLS connection (which shows whether a site uses a modern and secure protocol and ciphersuite), and subresource security (which indicates whether a site loads insecure HTTP subresources).