Currently on tmtest, any map that gets created is set to query location periodically (just using default frequency, whatever that is, which might be device-dependent). So if you haven't already enabled location for your browser for the site, it should ask then. I don't know why it would ask a second time when you try to get the position from Mapview's popup unless you don't click the "remember this" type of option.
So has anyone other than me been able to choose your location in the Mapview popup, or see your location on all the maps? I've added some console log messages, so if anyone is willing to try it out and can let me know if you're seeing some messages in the console, it might help figure out if I'm doing something incorrectly here. This is what I see in Firefox on successful use of geolocation in Mapview, with the last message repeated each time it queries my location again:
Enabling map.locate tmjsfuncs.js:316:13
mapLocationFound: created marker at LatLng(42.956189, -74.199605) tmjsfuncs.js:294:10
mapLocationFound: updated marker to LatLng(42.956189, -74.199605) tmjsfuncs.js:298:10
mapLocationFound: updated marker to LatLng(42.956183, -74.199612) tmjsfuncs.js:298:10
mapLocationFound: updated marker to LatLng(42.956191, -74.199624) tmjsfuncs.js:298:10