I have seen the same issue when stopping the app and it was still running. When choosing the stop application option, it didn't close. I thought I clicked the button too many times (start deployment) and that I caused it, but with your post it might be a bug.
I use the latest version of Chrome.
I have noticed it aswell, mainly while developing (6.8.1) . It seems to happen (more often?) after ''Running locally'' on a application that was allready running. Maybe something to do with refreshing the page? I haven't seen it happen after I shut down and redeploy.