Remove unused varibles. Cause compiler warnings.

Test Plan: make check

Reviewers: dhruba

Reviewed By: dhruba

CC: emayanke

Differential Revision: https://reviews.facebook.net/D6993

db/db_impl.cc

@@ -669,8 +669,6 @@ Status DBImpl::WriteLevel0TableForRecovery(MemTable* mem, VersionEdit* edit) {
   // should not be added to the manifest.
   int level = 0;
   if (s.ok() && meta.file_size > 0) {
-    const Slice min_user_key = meta.smallest.user_key();
-    const Slice max_user_key = meta.largest.user_key();
     edit->AddFile(level, meta.number, meta.file_size,
                   meta.smallest, meta.largest);
   }