Only prefer VP9 when experiments are actually enabled.

static/js/controllers/uicontroller.js

@@ -202,7 +202,7 @@ define(['jquery', 'underscore', 'bigscreen', 'moment', 'sjcl', 'modernizr', 'web
 		$scope.refreshWebrtcSettings = function() {
 			var settings = $scope.master.settings;
 			// Refresh SDP params.
-			if (settings.experimental.preferVideoSendCodecVP9) {
+			if (settings.experimental.enabled && settings.experimental.preferVideoSendCodecVP9) {
 				// Prefer VP9.
 				mediaStream.webrtc.settings.sdpParams.videoSendCodec = "VP9/90000";
 			} else {