UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/59.0.3071.115 Safari/537.36

Steps to reproduce the problem:
1. Open a site in chrome emulating a mobile device
2. Check window.navigator.userAgent with the console in the window context (e.g Nexus 6P "Mozilla/5.0 (Linux; Android 5.1.1; Nexus 6 Build/LYZ28E) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/59.0.3071.115 Mobile Safari/537.36")
3. Check self.navigator.userAgent in the service worker context (e.g Nexus 6P "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/59.0.3071.115 Safari/537.36")

What is the expected behavior?
The userAgent must be consistent in all the contexts (service worker, window) while we are emulating a device

What went wrong?
The userAgent is correctly set in the window context while you are emulating a mobile device but is not overrided in the service worker context (keeping the computer one)

Did this work before? N/A 

Chrome version: 59.0.3071.115  Channel: stable
OS Version: OS X 10.12.4
Flash Version: