message: Avoid some redundant indexing
  Summary:
  Do less work.
  This is a behavior-preserving change.
diff: @@ -420,10 +420,9 @@ size_t CrossDexRefMinimizer::erase(DexClass* cls, bool emitted, bool reset) {
  if (!emitted) {
  continue;
  }
  - if (m_applied_refs.count(ref) != 0) {
  + if (!m_applied_refs.insert(ref).second) {
  continue;
  }
  - m_applied_refs.emplace(ref);
  if (frequency == 0) {
  continue;
  }
  @@ -435,7 +434,6 @@ size_t CrossDexRefMinimizer::erase(DexClass* cls, bool emitted, bool reset) {
  // Updating m_class_infos and m_prioritized_classes
  m_class_infos.erase(class_info_it);
  - always_assert(m_class_infos.count(cls) == 0);
  }
  if (reset) {
  