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

tests/language/rewrite_if_return_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 = 2;
+}
+
+return_const(b) {
+    if (b) {
+        bar();
+        return 1;
+    } else {
+        baz();
+        return 1;
+    }
+}
+
+return_var(b, x) {
+    if (b) {
+        bar();
+        return x;
+    } else {
+        baz();
+        return x;
+    }
+}
+
+main() {
+    return_const(true);
+    Expect.equals(1, global);
+    return_const(false);
+    Expect.equals(2, global);
+
+    Expect.equals(4, return_var(true, 4));
+    Expect.equals(1, global);
+    Expect.equals(5, return_var(false, 5));
+    Expect.equals(2, global);
+}