In the wake of Google's announcement that it will start giving a ranking boost to full-SSL sites, many companies are converting their sites to be full-https. In wake of this, it's useful to check whether the resources (scripts, images, etc.) on your page are being loaded over http or https in preparation for converting your site.
While you could technically view the source of a file and use CMD-F (or CTRL-F) to search for http:// or https://, this is not a preferable solution since the page source is not the full rendered version of the file. For example, there may be CSS or JS files on the page which load non-secure images. Therefore, using the Chrome Developer Console is the best option.