temp stash

com.unity.uiwidgets/Runtime/gestures/mouse_tracking.cs

             MouseDetectorAnnotationFinder annotationFinder
             
         ) {
-            D.assert(_router != null);
+            D.assert(router != null);
             D.assert(annotationFinder != null);
             _router = router;
             router.addGlobalRoute(_handleEvent);
             if (Event is PointerSignalEvent)
                 return;
             int device = Event.device;
-            _MouseState existingState = _mouseStates[device];
+            _MouseState existingState = _mouseStates.getOrDefault(device);
             if (!_shouldMarkStateDirty(existingState, Event))
                 return;
             PointerEvent previousEvent = existingState?.latestEvent;
             
             _MouseState targetState = null;
             if (targetEvent != null) {
-              targetState = _mouseStates[targetEvent.device];
+              targetState = _mouseStates.getOrDefault(targetEvent.device);
               if (targetState == null) {
                 targetState = new  _MouseState(initialEvent: targetEvent);
                 _mouseStates[targetState.device] = targetState;

com.unity.uiwidgets/Runtime/widgets/binding.cs

     }
 
     public class WidgetsBinding : RendererBinding {
-        public static WidgetsBinding instance {
-            get { return _instance; }
+        public new static WidgetsBinding instance {
+            get { return (WidgetsBinding) RendererBinding.instance; }
-        static WidgetsBinding _instance;
 
         protected override void initInstances() {
             base.initInstances();
             get { return _buildOwner; }
         }
 
-        BuildOwner _buildOwner = new BuildOwner();
+        BuildOwner _buildOwner;
 
         public FocusManager focusManager {
             get { return _buildOwner.focusManager; }
     public class UiWidgetsBinding : WidgetsBinding {
         // todo 
         public static WidgetsBinding ensureInitialized() {
-            if (WidgetsBinding.instance == null)
-                new UiWidgetsBinding();
+            if (WidgetsBinding.instance == null) {
+                return new UiWidgetsBinding();
+            }
+            
             return WidgetsBinding.instance;
         }
     }