google.maps.places is undefined

You should add the option libraries=places in the Google API URL

In your case you should replace the following:

<script type="text/javascript" src="https://maps.googleapis.com/maps/api/js?v=3&key=....&sensor=false&callback=initializeMap"></script>

With this:

<script type="text/javascript" src="https://maps.googleapis.com/maps/api/js?v=3&key=....&sensor=false&callback=initializeMap&libraries=places"></script>

Look at the end of the src=""