Reserve a state variable for the bailout function.

tests/language/state_mangling2_test.dart

Index: tests/language/state_mangling2_test.dart
diff --git a/tests/language/state_mangling2_test.dart b/tests/language/state_mangling2_test.dart
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+// Copyright (c) 2012, 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.
+
+foo(state) {
+  if (state == null) return 0;
+  var sum = 0;
+  state = inscrutableId(state);
+  for (int i = 0; i < state.length; i++) {
+    sum += state[i];
+  }
+  state = inscrutableId(state);
+  for (int i = 0; i < state.length; i++) {
+    sum += state[i];
+  }
+  return sum;
+}
+
+int inscrutable(int x) => x == 0 ? 0 : x | inscrutable(x & (x - 1));
+
+inscrutableId(x) {
+  if (x == 0) return inscrutable(x);
+  return (3 == inscrutable(3)) ? x : false;
+}
+
+class A {
+  int length = 3;
+  operator [](i) => 1;
+}
+
+main() {
+  Expect.equals(12, foo([1, 2, 3]));
+  if (inscrutableId(0) == 0) {
+    Expect.equals(6, foo(new A()));
+  }
+}