Speed up _wouldBeTooManyUsers.
Speed up _wouldBeTooManyUsers.

On my current dart-program, this reduced compilation time by a third.

$ # before applying the patch:
$ time sdk/bin/dart2js --packages=sdk/.packages --out=/tmp/foo.js /tmp/bug2.dart
Dart file (/tmp/bug2.dart) compiled to JavaScript: /tmp/foo.js

real    0m29.859s
user    0m33.931s
sys     0m1.530s

$ time sdk/bin/dart2js --packages=sdk/.packages --out=/tmp/foo.js /tmp/bug2.dart
Dart file (/tmp/bug2.dart) compiled to JavaScript: /tmp/foo.js

real    0m30.062s
user    0m34.012s
sys     0m1.558s

$ # ----------------- apply the patch.
$ git stash pop

$ time sdk/bin/dart2js --packages=sdk/.packages --out=/tmp/foo.js /tmp/bug2.dart
Dart file (/tmp/bug2.dart) compiled to JavaScript: /tmp/foo.js

real    0m20.782s
user    0m24.540s
sys     0m1.750s

$ time sdk/bin/dart2js --packages=sdk/.packages --out=/tmp/foo.js /tmp/bug2.dart
Dart file (/tmp/bug2.dart) compiled to JavaScript: /tmp/foo.js

real    0m21.042s
user    0m24.495s
sys     0m2.173s

BUG=
R=sigmund@google.com

Review-Url: https://codereview.chromium.org/2602863002 .

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