CPU profiler: sample call stack on profiling start.

src/unbound-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
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 64 matching lines @@
 
 
 template<typename Record>
 void UnboundQueue<Record>::Enqueue(const Record& rec) {
   Node*& next = reinterpret_cast<Node*>(last_)->next;
   next = new Node(rec);
   OS::ReleaseStore(&last_, reinterpret_cast<AtomicWord>(next));
   while (first_ != reinterpret_cast<Node*>(divider_)) DeleteFirst();
 }
 
+
+template<typename Record>
+Record* UnboundQueue<Record>::Peek() {
+  ASSERT(divider_ != last_);
+  Node* next = reinterpret_cast<Node*>(divider_)->next;
+  return &next->value;
+}
+
 } }  // namespace v8::internal
 
 #endif  // V8_UNBOUND_QUEUE_INL_H_