[WIP] firebase init Error

sdk-intergration/LocalPackages/com.neuecc.unirx/Scripts/Operators/SynchronizedObserver.cs

@@ -0,0 +1,40 @@
+using System;
+
+namespace UniRx.Operators
+{
+    internal class SynchronizedObserver<T> : IObserver<T>
+    {
+        readonly IObserver<T> observer;
+        readonly object gate;
+
+        public SynchronizedObserver(IObserver<T> observer, object gate)
+        {
+            this.observer = observer;
+            this.gate = gate;
+        }
+
+        public void OnNext(T value)
+        {
+            lock (gate)
+            {
+                observer.OnNext(value);
+            }
+        }
+
+        public void OnError(Exception error)
+        {
+            lock (gate)
+            {
+                observer.OnError(error);
+            }
+        }
+
+        public void OnCompleted()
+        {
+            lock (gate)
+            {
+                observer.OnCompleted();
+            }
+        }
+    }
+}