Fix data race in v8::internal::UnboundQueue

src/unbound-queue.h

 // Copyright 2010 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 28 matching lines @@
 // consumer. Doesn't have restrictions on the number of queued
 // elements, so producer never blocks.  Implemented after Herb
 // Sutter's article:
 // http://www.ddj.com/high-performance-computing/210604448
 template<typename Record>
 class UnboundQueue BASE_EMBEDDED {
  public:
   inline UnboundQueue();
   inline ~UnboundQueue();
 
-  INLINE(void Dequeue(Record* rec));
+  INLINE(bool Dequeue(Record* rec));
   INLINE(void Enqueue(const Record& rec));
-  INLINE(bool IsEmpty()) { return divider_ == last_; }
-  INLINE(Record* Peek());
+  INLINE(bool IsEmpty() const);
+  INLINE(Record* Peek() const);
 
  private:
   INLINE(void DeleteFirst());
 
   struct Node;
 
   Node* first_;
   AtomicWord divider_;  // Node*
   AtomicWord last_;     // Node*
 
   DISALLOW_COPY_AND_ASSIGN(UnboundQueue);
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_UNBOUND_QUEUE_