Remove need to instantiate Platform and make methods static.

utils/tests/pub/test_pub.dart

Index: utils/tests/pub/test_pub.dart
diff --git a/utils/tests/pub/test_pub.dart b/utils/tests/pub/test_pub.dart
index 3d75640b45b48d4412598c958fc4e7ae02f5abf0..c37483de62c768207e008536f7d464befc58a2cf 100644
--- a/utils/tests/pub/test_pub.dart
+++ b/utils/tests/pub/test_pub.dart
@@ -21,7 +21,7 @@ void testOutput(String description, List<String> pubArgs, String expected,
     // Find a dart executable we can use to run pub. Uses the one that the
     // test infrastructure uses.
     final scriptDir = new File(new Options().script).directorySync().path;
-    final platform = new Platform().operatingSystem();
+    final platform = Platform.operatingSystem();
     final dartBin = joinPaths(scriptDir,
         '../../../tools/testing/bin/$platform/dart');