ConcurrencyAbstractionLayerImpl.FastPeriodicTimer and PeriodicTimer: …

…Allow delegate caching.

Rx.NET/Source/src/System.Reactive/Concurrency/ConcurrencyAbstractionLayerImpl.cs

@@ -194,13 +194,18 @@ public PeriodicTimer(Action action, TimeSpan period)
                 _action = action;
 
                 //
-                // Rooting of the timer happens through the this.Tick delegate's target object,
+                // Rooting of the timer happens through the timer's state
                 // which is the current instance and has a field to store the Timer instance.
                 //
-                _timer = new System.Threading.Timer(Tick, null, period, period);
+                _timer = new System.Threading.Timer(_ => Tick(_), this, period, period);
             }
 
-            private void Tick(object state) => _action();
+            private static void Tick(object state)
+            {
+                var timer = (PeriodicTimer)state;
+
+                timer._action();
+            }
 
             public void Dispose()
             {
@@ -224,19 +229,21 @@ public FastPeriodicTimer(Action action)
             {
                 _action = action;
 
-                new System.Threading.Thread(Loop)
+                new System.Threading.Thread(_ => Loop(_))
                 {
                     Name = "Rx-FastPeriodicTimer",
                     IsBackground = true
                 }
-                .Start();
+                .Start(this);
             }
 
-            private void Loop()
+            private static void Loop(object threadParam)
             {
-                while (!disposed)
+                var timer = (FastPeriodicTimer)threadParam;
+
+                while (!timer.disposed)
                 {
-                    _action();
+                    timer._action();
                 }
             }