Rate limit the number of gsutil.py subprocesses tools/approve_results.dart spawns
Rate limit the number of gsutil.py subprocesses tools/approve_results.dart spawns

Without any rate limiting, the `tools/approve_results.dart` tool can
render a machine unusable (e.g. when running with
`tools/approve_results.dart -b '*'`).

Unfortunately each gsutil.py subprocess might launch many more
subprocesses on it's own due to us passing the '-m' flag.

Change-Id: I06f4f54fb87a107d83d34205dafe03a8c73d747d
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/106902
Reviewed-by: Jonas Termansen <092ec58085ae5e368bc39d18752740ff81a2d09c@google.com>
Auto-Submit: Martin Kustermann <a35dd5b79fac84b2bb3b026a16b8becc55af5961@google.com>
Commit-Queue: Martin Kustermann <a35dd5b79fac84b2bb3b026a16b8becc55af5961@google.com>

dart-archive/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-lang/sdk,dartino/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk