Fix braino that lead to dead code that contained a typo. Also add a regression test.

tests/compiler/dart2js/interceptor_test.dart

+// Copyright (c) 2013, 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 'compiler_helper.dart';
+
+const String TEST_ONE = r"""
+  foo(a) {
+    // Make sure there is a bailout version.
+    foo(a);
+    // This will make a one shot interceptor that will be optimized in
+    // the non-bailout version because we know a is a number.
+    return (a + 42).toString;
+  }
+""";
+
+main() {
+  var generated = compile(TEST_ONE, entry: 'foo');
+  // Check that the one shot interceptor got converted to a direct
+  // call to the interceptor object.
+  Expect.isTrue(generated.contains('CONSTANT.get\$toString(a + 42);'));
+}