Revert "No need to allocate a new head node."

This reverts commit 46f9138.

Author: abersnaze

src/main/java/rx/internal/operators/OperatorReplay.java

@@ -897,24 +897,29 @@ final void removeFirst() {
             size--;
             // can't just move the head because it would retain the very first value
             // can't null out the head's value because of late replayers would see null
-            setFirst(next);
+            setFirst(next.get());
         }
-        /* test */ final void removeSome(int n) {
+        final void removeSome(int n) {
             Node head = get();
             while (n > 0) {
                 head = head.get();
                 n--;
                 size--;
             }
 
-            setFirst(head);
+            setFirst(head.get());
         }
         /**
          * Arranges the given node is the new head from now on.
          * @param n
          */
         final void setFirst(Node n) {
-            set(n);
+            Node newHead = new Node(null);
+            newHead.lazySet(n);
+            if (n == null) {
+                tail = newHead;
+            }
+            set(newHead);
         }
 
         @Override
@@ -1114,23 +1119,21 @@ Object leaveTransform(Object value) {
         void truncate() {
             long timeLimit = scheduler.now() - maxAgeInMillis;
 
-            Node prev = get();
-            Node next = prev.get();
+            Node head = get();
+            Node next = head.get();
 
             int e = 0;
             for (;;) {
                 if (next != null) {
                     if (size > limit) {
                         e++;
                         size--;
-                        prev = next;
                         next = next.get();
                     } else {
                         Timestamped<?> v = (Timestamped<?>)next.value;
                         if (v.getTimestampMillis() <= timeLimit) {
                             e++;
                             size--;
-                            prev = next;
                             next = next.get();
                         } else {
                             break;
@@ -1141,15 +1144,15 @@ void truncate() {
                 }
             }
             if (e != 0) {
-                setFirst(prev);
+                setFirst(next);
             }
         }
         @Override
         void truncateFinal() {
             long timeLimit = scheduler.now() - maxAgeInMillis;
 
-            Node prev = get();
-            Node next = prev.get();
+            Node head = get();
+            Node next = head.get();
 
             int e = 0;
             for (;;) {
@@ -1158,7 +1161,6 @@ void truncateFinal() {
                     if (v.getTimestampMillis() <= timeLimit) {
                         e++;
                         size--;
-                        prev = next;
                         next = next.get();
                     } else {
                         break;
@@ -1168,7 +1170,7 @@ void truncateFinal() {
                 }
             }
             if (e != 0) {
-                setFirst(prev);
+                setFirst(next);
             }
         }
     }