Closures going into shared variables in particular have to be confirmed to capture appropriate values.
BUG=https://github.com/dart-lang/sdk/issues/62179
TEST=run_isolate_group_run_test
Cq-Include-Trybots: luci.dart.try:vm-dyn-linux-debug-x64-try,vm-dyn-mac-debug-arm64-try,vm-aot-dyn-linux-debug-x64-try
Change-Id: I27416773fd77077018739ea4dbcc6e4695e67be8
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/469103
Reviewed-by: Alexander Markov <alexmarkov@google.com>
Commit-Queue: Alexander Aprelev <aam@google.com>