Squashed 'src/leveldb/' changes from cad64b151d..ab6c84e6f3

ab6c84e6f3 Merge bitcoin-core/leveldb-subtree#58: Initialize file_size to 0 to avoid UB
ad9b1c9893 Initialize file_size to 0 to avoid UB

git-subtree-dir: src/leveldb
git-subtree-split: ab6c84e6f38fae0279e30305a182f9b4674e2ecd

db/db_impl.cc

@@ -803,6 +803,7 @@ Status DBImpl::OpenCompactionOutputFile(CompactionState* compact) {
     pending_outputs_.insert(file_number);
     CompactionState::Output out;
     out.number = file_number;
+    out.file_size = 0;
     out.smallest.Clear();
     out.largest.Clear();
     compact->outputs.push_back(out);