Add multithreading test for SamplingCircularQueue, fix implementation.

src/circular-queue-inl.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
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@@ skipping 64 matching lines @@
 }
 
 
 template<typename Record>
 Record* CircularQueue<Record>::Next(Record* curr) {
   return ++curr != buffer_end_ ? curr : buffer_;
 }
 
 
 void* SamplingCircularQueue::Enqueue() {
-  Cell* enqueue_pos = reinterpret_cast<Cell*>(
-      Thread::GetThreadLocal(producer_key_));
-  WrapPositionIfNeeded(&enqueue_pos);
-  Thread::SetThreadLocal(producer_key_, enqueue_pos + record_size_);
-  return enqueue_pos;
+  WrapPositionIfNeeded(&producer_pos_->enqueue_pos);
+  void* result = producer_pos_->enqueue_pos;
+  producer_pos_->enqueue_pos += record_size_;
+  return result;
 }
 
 
 void SamplingCircularQueue::WrapPositionIfNeeded(
     SamplingCircularQueue::Cell** pos) {
   if (**pos == kEnd) *pos = buffer_;
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_CIRCULAR_BUFFER_INL_H_