Android app restriction is not valid for Google Maps JavaScript API. This restriction is only used with Google Maps Android SDK and Places Android SDK.
Have a look at the following document that explains which type of API key restriction you can use with Google Maps APIs
https://developers.google.com/maps/faq#keysystem
In order to solve your issue, I would suggest checking the value of window.location.href in your HTML page when you load it from Web view in your Android app. This value will contain string that might be used as HTTP referrer restriction for Maps JavaScript API. Note that file:// protocol requires special representation as explained in
https://developers.google.com/maps/documentation/javascript/get-api-key#key-restrictions
I hope this helps!
