Add lock-based unbounded queue

src/locked-queue.h

Index: src/locked-queue.h
diff --git a/src/locked-queue.h b/src/locked-queue.h
new file mode 100644
index 0000000000000000000000000000000000000000..5bb97c8a125132d012a8e0671d08878d4aa36b4b
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+++ b/src/locked-queue.h
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+// Copyright 2015 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef V8_LOCKED_QUEUE_
+#define V8_LOCKED_QUEUE_
+
+#include "src/allocation.h"
+#include "src/base/platform/platform.h"
+
+namespace v8 {
+namespace internal {
+
+// Simple lock-based unbounded size queue (multi producer; multi consumer) based
+// on "Simple, Fast, and Practical Non-Blocking and Blocking Concurrent Queue
+// Algorithms" by M. Scott and M. Michael.
+// See:
+// https://www.cs.rochester.edu/research/synchronization/pseudocode/queues.html
+template <typename Record>
+class LockedQueue final BASE_EMBEDDED {
+ public:
+  inline LockedQueue();
+  inline ~LockedQueue();
+  inline void Enqueue(const Record& record);
+  inline bool Dequeue(Record* record);
+  inline bool IsEmpty() const;
+  inline bool Peek(Record* record) const;
+
+ private:
+  struct Node;
+
+  mutable base::Mutex head_mutex_;
+  base::Mutex tail_mutex_;
+  Node* head_;
+  Node* tail_;
+
+  DISALLOW_COPY_AND_ASSIGN(LockedQueue);
+};
+
+}  // namespace internal
+}  // namespace v8
+
+#endif  // V8_LOCKED_QUEUE_