Fix bug in dart2js where the return type in a bailout version was not registered.

tests/language/bailout3_test.dart

+// 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.
+
+// Test that the return type of a method is being registered for both
+// its bailout and optimized version in dart2js.
+
+var a;
+
+bar() {
+  if (a[0] == 0) {
+    // Force bailout version.
+    bar();
+    // Avoid inlining.
+    throw 0;
+  }
+  for (int i = 0; i < 10; i++) {
+    a[0] = 42;
+  }
+  // This return should say that bar can return an array or unknown.
+  return a;
+}
+
+foo() {
+  if (a[0] == 0) {
+    // Avoid inlining.
+    throw 0;
+  }
+  var a = bar();
+  // This check used to fail because dart2js was assuming [a] was an
+  // array.
+  Expect.equals(1, a.length);
+}
+
+main() {
+  a = new Map();
+  bar();
+  foo();
+}