message: `reserve` in DexIdx
  Summary: As title. Avoid reallocation.
diff: @@ -169,6 +169,7 @@ DexTypeList* DexIdx::get_type_list(uint32_t offset) {
  uint32_t size = *tlp++;
  const uint16_t* typep = (const uint16_t*)tlp;
  DexTypeList::ContainerType tlist;
  + tlist.reserve(size);
  for (uint32_t i = 0; i < size; i++) {
  tlist.push_back(get_typeidx(typep[i]));
  }
  