4a222e0924
Hide constructors of types objects and avoid creating extra instances of types, caching them as necessary. TEST=existing Change-Id: I2897888649dd1c4338d6e4000ab0c481d9da3c01 Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/308242 Reviewed-by: Slava Egorov <vegorov@google.com> Commit-Queue: Alexander Markov <alexmarkov@google.com>