Chrome getUserMedia Not Requesting Permission Locally
Chrome blocks a lot of stuff on file:/// URIs without reporting a security error (eg. Geolocation). Your best option is to run from a local webserver, if you have Python installed try SimpleHTTPServer.
Google chrome DOMException: Permission denied by system for navigator.mediaDevices.getUserMedia
Since MacOS Mojave, camera and microphone require OS permissions.
This applies to all non-Apple products, including all browsers other than Safari.
Check System Preferences > Security & Privacy > Privacy > Camera & Microphone. Make sure Chrome is listed and has a checkbox.
You should have gotten a special OS prompt about this the first time Chrome tried to access them. But if it accidentally got blocked somehow, you won't ever be prompted again.
getUserMedia() permission denied
The second demo you mentioned (this one) works for me on Chrome 28.
It sounds like you enabled the flag, but make sure the one called Enable screen capture support in getUserMedia() is enabled in chrome://flags (and that you have restarted Chrome since enabling that).
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