demo.js assumes that unprefixed MediaStream is Firefox-only

[foolip]

getUserMedia.js/face-detection-demo/js/demo.js

Line 124 in a0f839a

if ((typeof MediaStream !== "undefined" && MediaStream !== null) && stream instanceof MediaStream) {

This code uses (typeof MediaStream !== "undefined" && MediaStream !== null) && stream instanceof MediaStream as the guard for a Firefox-only code path, where either video.mozSrcObject must be supported or one must support assigning a MediaStream instance to video.src. Neither on a path to standardization, only srcObject is.

This has broken the demo in Chrome 55, where I exposed the unprefixed MediaStream interface:
https://bugs.chromium.org/p/chromium/issues/detail?id=674608
https://bugs.chromium.org/p/chromium/issues/detail?id=649331

@alvestrand @henbos @guidou FYI