UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.11; rv:55.0) Gecko/20100101 Firefox/55.0
Platform: 9592.85.0 (Official Build) stable-channel link

Steps to reproduce the problem:
1. Make a call to chooseDesktopMedia and choose tab
2. Choose a tab with static content - nothing can move within the tab, including the mouse
3. Start recording the stream you got from chooseDesktopMedia
4. Resulting recorder will not be able to record anything from the stream

Here is an example app that can show the behavior:
https://github.com/niklasenbom/RecordingApp

What is the expected behavior?
The stream returned by chooseDesktopMedia for a tab streams static content

What went wrong?
It appears as if the stream returned does not start until motion on the tab is detected

Did this work before? N/A 

Does this work in other browsers? N/A

Chrome version: 60.0.3112.112  Channel: stable
OS Version: 60.0.3112.112
Flash Version: 26.0.0.151

I originally thought this might have been a bug in the recorder, but the work-around is to display a small animation in the corner of the tab while recording.  This makes me think it might be a Chrome issue.

https://github.com/muaz-khan/Chrome-Extensions/commit/840da08c5dd64f32e6ccea7d1854e50b653a8c30