Move hash.h/cc from net/disk_cache to base.

net/disk_cache/hash.h

-// Copyright (c) 2011 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_DISK_CACHE_HASH_H__
-#define NET_DISK_CACHE_HASH_H__
-
-#include <string>
-
-#include "base/basictypes.h"
-#include "net/base/net_export.h"
-
-namespace disk_cache {
-
-// From http://www.azillionmonkeys.com/qed/hash.html
-// This is the hash used on WebCore/platform/stringhash
-NET_EXPORT_PRIVATE uint32 SuperFastHash(const char * data, int len);
-
-inline uint32 Hash(const char* key, size_t length) {
-  return SuperFastHash(key, static_cast<int>(length));
-}
-
-inline uint32 Hash(const std::string& key) {
-  if (key.empty())
-    return 0;
-  return SuperFastHash(key.data(), static_cast<int>(key.size()));
-}
-
-}  // namespace disk_cache
-
-#endif  // NET_DISK_CACHE_HASH_H__