Use closure conversion in new dart2js backend.

tests/compiler/dart2js/js_backend_cps_ir_closures.dart

+// Copyright (c) 2014, 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 of interceptors.
+
+library closures_test;
+
+import 'js_backend_cps_ir_test.dart';
+
+const List<TestEntry> tests = const [
+  const TestEntry("""
+main(x) {
+  a() {
+    return x;
+  }
+  x = x + '1';
+  print(a());
+}
+""",
+r"""
+function(x) {
+  var box_0, a, v0;
+  box_0 = {};
+  box_0.x_0 = x;
+  a = new V.main_a(box_0);
+  x = box_0.x_0;
+  v0 = "1";
+  box_0.x_0 = J.getInterceptor(x).$add(x, v0);
+  P.print(a.call$0());
+  return null;
+}"""),
+
+  const TestEntry("""
+main(x) {
+  a() {
+    return x;
+  }
+  print(a());
+}
+""",
+r"""
+function(x) {
+  P.print(new V.main_a(x).call$0());
+  return null;
+}"""),
+
+  const TestEntry("""
+main() {
+  var x = 122;
+  var a = () => x;
+  x = x + 1;
+  print(a());
+}
+""",
+r"""
+function() {
+  var box_0, a, x, v0;
+  box_0 = {};
+  box_0.x_0 = 122;
+  a = new V.main_closure(box_0);
+  x = box_0.x_0;
+  v0 = 1;
+  box_0.x_0 = J.getInterceptor(x).$add(x, v0);
+  P.print(a.call$0());
+  return null;
+}"""),
+
+  const TestEntry("""
+main() {
+  var x = 122;
+  var a = () {
+    var y = x;
+    return () => y;
+  };
+  x = x + 1;
+  print(a()());
+}
+""",
+r"""
+function() {
+  var box_0, a, x, v0;
+  box_0 = {};
+  box_0.x_0 = 122;
+  a = new V.main_closure(box_0);
+  x = box_0.x_0;
+  v0 = 1;
+  box_0.x_0 = J.getInterceptor(x).$add(x, v0);
+  P.print(a.call$0().call$0());
+  return null;
+}"""),
+
+  const TestEntry("""
+main() {
+  var a;
+  for (var i=0; i<10; i++) {
+    a = () => i;
+  }
+  print(a());
+}
+""",
+r"""
+function() {
+  var a, box_0, i, v0, box_01, v1;
+  a = null;
+  box_0 = {};
+  box_0.i_0 = 0;
+  while (true) {
+    i = box_0.i_0;
+    v0 = 10;
+    if (P.identical(J.getInterceptor(i).$lt(i, v0), true)) {
+      a = new V.main_closure(box_0);
+      box_01 = {};
+      box_01.i_0 = box_0.i_0;
+      i = box_01.i_0;
+      v1 = 1;
+      box_01.i_0 = J.getInterceptor(i).$add(i, v1);
+      box_0 = box_01;
+    } else {
+      P.print(a.call$0());
+      return null;
+    }
+  }
+}"""),
+];