CPU profiler: sample call stack on profiling start.

src/unbound-queue-inl.h

Index: src/unbound-queue-inl.h
diff --git a/src/unbound-queue-inl.h b/src/unbound-queue-inl.h
index ff5d8338305fc8235531fd9c46e6c8dbe65bf8f7..fffb1dbcfb13d966c2164d19dc781404c976af52 100644
--- a/src/unbound-queue-inl.h
+++ b/src/unbound-queue-inl.h
@@ -82,6 +82,14 @@ void UnboundQueue<Record>::Enqueue(const Record& rec) {
   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_