Merge kernel closure conversion into the Dart SDK

pkg/kernel/testcases/closures/for_loop.dart

+// Copyright (c) 2016, 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.md file.
+
+const int max = 100;
+
+main() {
+  var closures = [];
+  var closures2 = [];
+  var last;
+  for (int i = 0; i < max; i++) {
+    closures.add(() => last = i);
+    closures2.add(() {
+      if (last != max - 1) throw "last: $last != ${max - 1}";
+    });
+  }
+  int sum = 0;
+  for (Function f in closures) {
+    sum += f();
+  }
+  for (Function f in closures2) {
+    f();
+  }
+  // This formula is credited to Gauss. Search for "Gauss adding 1 to 100".
+  int expectedSum = (max - 1) * max ~/ 2;
+  if (expectedSum != sum) {
+    throw new Exception("Unexpected sum = $sum != $expectedSum");
+  }
+}