Add test for scope accessed by multiple closures.

tests/language/src/ClosureSharedStateTest.dart

+// Copyright (c) 2011, 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.
+
+// Tests for closures sharing mutable bindings.
+
+var f;
+var g;
+
+setupPlain() {
+  int j = 1000;
+  // Two closures sharing variable 'j'; j initially is 1000.
+  f = (int x) { var q = j; j = x; return q;};
+  g = (int x) { var q = j; j = x; return q;};
+}
+
+setupLoop() {
+  for (int i = 0; i < 2; i++) {
+    int j = i * 1000;  // The last stored closure has j initially 1000.
+    // Two closures sharing variable 'j'.
+    f = (int x) { var q = j; j = x; return q;};
+    g = (int x) { var q = j; j = x; return q;};
+  }
+}
+
+setupNestedLoop() {
+  for (int outer = 0; outer < 2; outer++) {
+    int j = outer * 1000;
+    for (int i = 0; i < 2; i++) {
+      // Two closures sharing variable 'j' in a loop at different nesting.
+      f = (int x) { var q = j; j = x; return q;};
+      g = (int x) { var q = j; j = x; return q;};
+    }
+  }
+}
+
+test(setup) {
+  setup();
+  Expect.equals(1000, f(100));
+  Expect.equals(100, f(200));
+  Expect.equals(200, f(300));
+  Expect.equals(300, g(400));
+  Expect.equals(400, g(500));
+}
+
+
+main() {
+  test(setupPlain);
+  test(setupLoop);
+  test(setupNestedLoop);
+}