Revert of DEPS: Update leveldatabase from 1.18 to 1.20.

third_party/leveldatabase/port/port_chromium.h

Index: third_party/leveldatabase/port/port_chromium.h
diff --git a/third_party/leveldatabase/port/port_chromium.h b/third_party/leveldatabase/port/port_chromium.h
index 3dc2d986c892da990e8b113b24f9ed5c00393803..557945318f6493dedab9f5b4749f8b1ed9cfc6cf 100644
--- a/third_party/leveldatabase/port/port_chromium.h
+++ b/third_party/leveldatabase/port/port_chromium.h
@@ -115,10 +115,7 @@
   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_