fix facingMode for mobile device.

Author: cloudwebrtc

lib/src/mediadevices_impl.dart

@@ -5,14 +5,16 @@ import 'dart:js_util' as jsutil;
 import 'package:webrtc_interface/webrtc_interface.dart';
 
 import 'media_stream_impl.dart';
+import 'utils.dart';
 
 class MediaDevicesWeb extends MediaDevices {
   @override
   Future<MediaStream> getUserMedia(
       Map<String, dynamic> mediaConstraints) async {
     try {
-      if (mediaConstraints['video'] is Map) {
-        if (mediaConstraints['video']['facingMode'] != null) {
+      if (!isMobile) {
+        if (mediaConstraints['video'] is Map &&
+            mediaConstraints['video']['facingMode'] != null) {
           mediaConstraints['video'].remove('facingMode');
         }
       }

lib/src/utils.dart

@@ -0,0 +1,16 @@
+import 'dart:html' as html;
+
+bool get isMobile {
+  final toMatch = [
+    'Android',
+    'webOS',
+    'iPhone',
+    'iPad',
+    'iPod',
+    'BlackBerry',
+    'Windows Phone'
+  ];
+  return toMatch.indexWhere((device) => html.window.navigator.userAgent
+          .contains(RegExp(device, caseSensitive: false))) !=
+      -1;
+}