(In reply to Jan-Ivar Bruaroey [:jib] (needinfo? me) from comment #5)
We have [tests in the
test_getUserMedia_basicScreenshare.html#100,119) for verifying that screen
capture from content works. Screen capture is easier to test than cameras.
Our screen-capture prompts' preview area is implemented using screen capture
from chrome, i.e. verifiable through manual testing—We have automated tests
for these capture calls succeeding, but not for verifying that actual pixels
appear. In any case, it should be doable without code insertion.
I don't know which calls specifically needed to be on the UI thread, maybe
I don't think any of these calls need to be on a ui thread. We originally implemented this thinking some of this capture stuff needed a ui pump. After implementing it we realized the real culprit was the compositor background thread, which created windows but didn't pump.