leveldb: Reuse manifest (AKA logs) during open.

third_party/leveldatabase/env_chromium.h

Index: third_party/leveldatabase/env_chromium.h
diff --git a/third_party/leveldatabase/env_chromium.h b/third_party/leveldatabase/env_chromium.h
index 52a6f48d6cd90f75651788a5a09007b21c0d58cc..5372ac8f9910c5c971dee901576fd2873c73d7cd 100644
--- a/third_party/leveldatabase/env_chromium.h
+++ b/third_party/leveldatabase/env_chromium.h
@@ -47,6 +47,11 @@ enum MethodID {
   kNumEntries
 };
 
+// The default value for leveldb::Options::reuse_logs. Currently log reuse is an
+// experimental feature in leveldb. More info at:
+// https://github.com/google/leveldb/commit/251ebf5dc70129ad3
+const bool kDefaultLogReuseOptionValue = true;
+
 const char* MethodIDToString(MethodID method);
 
 leveldb::Status MakeIOError(leveldb::Slice filename,