Use `-O4` when compiling benchmarks. (#552)
Use `-O4` when compiling benchmarks. (#552)

`--omit-implicit-checks` and `--trust-primitives` are implied by `-O4`:

https://github.com/dart-lang/sdk/blob/40ad7aee40a82aba55a6a9481b9421c6785c9a2b/pkg/compiler/lib/src/options.dart#L784-L789

Co-authored-by: Loren Van Spronsen <84709c0807b4e2f6c888c444b808ad0fe2ec0417@google.com>
Co-authored-by: Ömer Sinan Ağacan <d15e39adaef0c3a64e4ea5d68f5c1b5be1f04e29@google.com>
dart-lang/dart-protobuf,dart-lang/protobuf,google/protobuf.dart,dart-lang/protobuf,dart-lang/dart-protobuf,dart-lang/protobuf,dart-lang/dart-protobuf,google/protobuf.dart,google/protobuf.dart