UserAgent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87 Safari/537.36

Steps to reproduce the problem:
1. open devtool for a web app with service worker enabled (e.g https://readiness.firebaseapp.com/main/entrepreneur)
2. under network, try to `copy > copy All as HAR` or `save as HAR with content` 

What is the expected behavior?
HAR information is exported (in the file and in the clipboard)

What went wrong?
both export (clipboard and file) are empty

Did this work before? N/A 

Chrome version: 56.0.2924.87  Channel: stable
OS Version: mint 18,1 Serena
Flash Version: 

HAR export is working on the first load (e.g. when service worker is not yet active)