void HeaderMapImpl::setCopy(const LowerCaseString& key, absl::string_view value) {
  // Replaces the first occurrence of a header if it exists, otherwise adds by copy.
  // TODO(#9221): converge on and document a policy for coalescing multiple headers.
  auto* entry = getExisting(key);
  if (entry) {
    updateSize(entry->value().size(), value.size());
    entry->value(value);
  } else {
    addCopy(key, value);
  }
}
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