wpGoogleMaps.php lines 213, 315 and 615. I attempted then manually loading it from https://maps.google.com, and it worked, so I figured a simple fix would to do the same thing Google itself does when loading Google Analytics, by changing those three lines from:
I tested this on 5.01 and it works perfectly: no more complaints from Google Chrome when loading the page from the HTTPS version!
I hope this helps. It'd be nice to have this added to the official plugin!
PS.: Naturally, an even simpler version would be: