message: Remove const which prevents copy elision.
diff: @@ -26,7 +26,7 @@ namespace {
  // An AEAD which will always return a kInternal status on API calls.
  class AlwaysFailAead : public Aead {
  public:
  - explicit AlwaysFailAead(const std::string message)
  + explicit AlwaysFailAead(std::string message)
  : message_(std::move(message)) {}
  crypto::tink::util::StatusOr<std::string> Encrypt(
  