Dart code did not expect OSError as a return value from Socket_GetPort.
This CL ensures that Dart code handles OSError in addition to int gracefully as a result of Socket_GetPort call.
Fixes https://github.com/dart-lang/sdk/issues/45116
TEST=run dart ci socket tests on mac with transparent proxy running
Change-Id: I198d99107729ccefecd9a16b71474ccdbfc0039b
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/193221
Reviewed-by: Siva Annamalai <asiva@google.com>
Commit-Queue: Alexander Aprelev <aam@google.com>
Alexander Aprelev