I don't go to HTTPS , I just type google.com or using history (http:\\google.com) , probably because I'm logged with my google account , it takes me to secured HTTPS.
The settings on my security zones are defualt.
I was using Avira before , now trying Kaspersky , and Avast for deciding my new AV. Both Avira and Kaspersky never shows that message , only Avast , If I disable the add-ons , the message won't pop.
If I logged out of my Google account , it won't pop up , and it's only happen with Avast , with add ons enabled . I used Kaspersky , with KS add ones enabled , it didn't show the message.
Maybe you should try logging in to your google account and visit google.com
Thanks Sharky7Sharky for the link , but I'm not sure if I should disable or enable mixed content , as the link says it sometimes needed for Java.