dart2dart: Test cases for better code coverage in dart_tree rewritings.

tests/language/rewrite_if_swap_test.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.
+
+import "package:expect/expect.dart";
+
+var global = 0;
+
+bar() {
+    global += 1;
+}
+baz() {
+    global += 100;
+}
+
+foo(b) {
+    var old_backend_was_used;
+    if (b ? false : true) {
+        bar();
+        bar();
+    } else {
+        baz();
+        baz();
+    }
+}
+
+main() {
+    foo(true);
+    Expect.equals(2, global);
+
+    foo(false);
+    Expect.equals(202, global);
+}