Start 'fuzzing' of dart:io APIs and fix first issue found.

tests/standalone/io/file_fuzz_test.dart

+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+// 'fuzz' test the file APIs by providing unexpected type arguments. The test
+// passes if the VM does not crash.
+
+#import('dart:io');
+
+final typeMapping = const {
+  'int': 0,
+  'String': 'a',
+  'FileMode': FileMode.READ,
+  'num': 0.50,
+  'List<int>': const [1, 2, 3]
+};
+
+doItSync(Function f) {
+  // Ignore all exceptions.
+  try { f(); } catch (var e) {}
+}
+
+fuzzSyncMethods() {
+  typeMapping.forEach((k, v) {
+    doItSync(() {
+      var f = new File(v);
+      doItSync(f.existsSync);
+      doItSync(f.createSync);
+      doItSync(f.deleteSync);
+      doItSync(f.directorySync);
+      doItSync(f.lengthSync);
+      doItSync(f.fullPathSync);
+      doItSync(() => f.openInputStream().onError = (e) => null);
+      doItSync(f.readAsBytesSync);
+      typeMapping.forEach((k2, v2) {
+        doItSync(() => f.openSync(v2));
+        doItSync(() => f.openOutputStream(v2).onError = (e) => null);
+        doItSync(() => f.readAsTextSync(v2));
+        doItSync(() => f.readAsLinesSync(v2));
+      });
+    });
+  });
+}
+
+main() {
+  fuzzSyncMethods();
+}