Support unittest of jumps

tests/compiler/dart2js/jumps/data/jump.dart

+// Copyright (c) 2017, 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.
+
+simpleForLoop(count) {
+  for (int i = 0; i < count; i = i + 1) {
+    print(i);
+  }
+}
+
+simpleForLoopWithBreak(count) {
+  /*0@break*/ for (int i = 0; i < count; i = i + 1) {
+    if (i % 2 == 0) /*target=0*/ break;
+    print(i);
+  }
+}
+
+main() {
+  simpleForLoop(10);
+  simpleForLoopWithBreak(10);
+}