Initialize the branches list with the right size

Change-Id: I643626b269f93b567df604def5e9ec233c74b16f
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/project/ListBranches.java b/gerrit-server/src/main/java/com/google/gerrit/server/project/ListBranches.java
index a370720..8195c2a 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/project/ListBranches.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/project/ListBranches.java
@@ -113,7 +113,7 @@
     try (Repository db = repoManager.openRepository(rsrc.getNameKey())) {
       Collection<Ref> heads =
           db.getRefDatabase().getRefs(Constants.R_HEADS).values();
-      refs = new ArrayList<>(heads.size() + 2);
+      refs = new ArrayList<>(heads.size() + 3);
       refs.addAll(heads);
       addRef(db, refs, Constants.HEAD);
       addRef(db, refs, RefNames.REFS_CONFIG);