UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.11; rv:53.0) Gecko/20100101 Firefox/53.0

Steps to reproduce the problem:
WebSocket frame viewer is broken similarly to  https://bugs.chromium.org/p/chromium/issues/detail?id=598076 which was fixed long ago. 

What is the expected behavior?

What went wrong?
WebSockets viewer flips back to a different resource on arrival of a new WS frame 

Did this work before? Yes 

Chrome version: 58.0.3029.81 (Official Build) (64-bit)  Channel: n/a
OS Version: OS X 10.11
Flash Version: Shockwave Flash 25.0.0.148