Imported Upstream version 4.6.0.125

Former-commit-id: a2155e9bd80020e49e72e86c44da02a8ac0e57a4

mcs/class/referencesource/System.Activities/System/Activities/Statements/ExecutionTracker.cs

@@ -0,0 +1,58 @@
+//----------------------------------------------------------------
+// Copyright (c) Microsoft Corporation.  All rights reserved.
+//----------------------------------------------------------------
+
+namespace System.Activities.Statements
+{
+    using System;
+    using System.Collections.Generic;
+    using System.Runtime.Serialization;
+
+    [DataContract]
+    sealed class ExecutionTracker
+    {
+        List<CompensationTokenData> executionOrderedList;
+
+        public ExecutionTracker()
+        {
+            this.executionOrderedList = new List<CompensationTokenData>();
+        }
+
+        public int Count
+        {
+            get
+            {
+                return this.executionOrderedList.Count;
+            }
+        }
+
+        [DataMember(Name = "executionOrderedList")]
+        internal List<CompensationTokenData> SerializedExecutionOrderedList
+        {
+            get { return this.executionOrderedList; }
+            set { this.executionOrderedList = value; }
+        }
+
+        public void Add(CompensationTokenData compensationToken)
+        {
+            this.executionOrderedList.Insert(0, compensationToken);
+        }
+
+        public void Remove(CompensationTokenData compensationToken)
+        {
+            this.executionOrderedList.Remove(compensationToken);
+        }
+
+        public CompensationTokenData Get()
+        {
+            if (Count > 0)
+            {
+                return this.executionOrderedList[0];
+            }
+            else
+            {
+                return null;
+            }
+        }
+    }
+}