Revert of DEPS: Update leveldatabase from 1.18 to 1.20.

third_party/leveldatabase/port/port_chromium.h

 // Copyright (c) 2011 The LevelDB Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file. See the AUTHORS file for names of contributors.
 //
 // See port_example.h for documentation for the following types/functions.
 
 #ifndef STORAGE_LEVELDB_PORT_PORT_CHROMIUM_H_
 #define STORAGE_LEVELDB_PORT_PORT_CHROMIUM_H_
 
 #include <stddef.h>
@@ skipping 97 matching lines @@
                      std::string* output);
 bool Snappy_GetUncompressedLength(const char* input, size_t length,
                                   size_t* result);
 bool Snappy_Uncompress(const char* input_data, size_t input_length,
                        char* output);
 
 inline bool GetHeapProfile(void (*func)(void*, const char*, int), void* arg) {
   return false;
 }
 
-// Implemented in leveldb's src/port/port_posix_sse.cc.
-uint32_t AcceleratedCRC32C(uint32_t crc, const char* buf, size_t size);
-
-}  // namespace port
-}  // namespace leveldb
+}
+}
 
 #endif  // STORAGE_LEVELDB_PORT_PORT_CHROMIUM_H_