Another option has been added, one that says "HTTPS Redirect". If this feature is turned on, automatically all visitors will be redirected to the HTTPS URL instead of the old insecure HTTP link.
Google also stated that mixed content may cause some of the blog's functionality no to work with the HTTPS version. This is usually caused by incompatible templates, gadgets, or post contents and they are working on these issues but there are some setting that blog owners only will be able to do so that these works.
Source:[Google Security Blog]