Add QuicLRUCache.

net/quic/platform/api/quic_lru_cache.h

Index: net/quic/platform/api/quic_lru_cache.h
diff --git a/net/quic/platform/api/quic_lru_cache.h b/net/quic/platform/api/quic_lru_cache.h
new file mode 100644
index 0000000000000000000000000000000000000000..b7a0623309cfa2c1840af0ee78d27e56e83ce334
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+++ b/net/quic/platform/api/quic_lru_cache.h
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+// Copyright (c) 2016 The Chromium 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 NET_QUIC_PLATFORM_API_QUIC_LRU_CACHE_H_
+#define NET_QUIC_PLATFORM_API_QUIC_LRU_CACHE_H_
+
+#include <memory>
+
+#include "net/quic/platform/impl/quic_lru_cache_impl.h"
+
+namespace net {
+
+// A LRU cache that maps from type Key to Value* in QUIC.
+// This cache CANNOT be shared by multiple threads (even with locks) because
+// Value* returned by Lookup() can be invalid if the entry is evicted by other
+// threads.
+template <class K, class V>
+class QuicLRUCache {
+ public:
+  explicit QuicLRUCache(int64_t total_units) : impl_(total_units) {}
+
+  // Inserts one unit of |key|, |value| pair to the cache. Cache takes ownership
+  // of inserted |value|.
+  void Insert(const K& key, std::unique_ptr<V> value) {
+    impl_.Insert(key, std::move(value));
+  }
+
+  // If cache contains an entry for |key|, return a pointer to it. This returned
+  // value is guaranteed to be valid until Insert or Clear.
+  // Else return nullptr.
+  V* Lookup(const K& key) { return impl_.Lookup(key); }
+
+  // Removes all entries from the cache. This method MUST be called before
+  // destruction.
+  void Clear() { impl_.Clear(); }
+
+  // Returns maximum size of the cache.
+  int64_t MaxSize() const { return impl_.MaxSize(); }
+
+  // Returns current size of the cache.
+  int64_t Size() const { return impl_.Size(); }
+
+ private:
+  QuicLRUCacheImpl<K, V> impl_;
+
+  DISALLOW_COPY_AND_ASSIGN(QuicLRUCache);
+};
+
+}  // namespace net
+
+#endif  // NET_QUIC_PLATFORM_API_QUIC_LRU_CACHE_H_