Fix async machinery (issue 22445 and possibly others to be triaged later).

tests/language/regress_22445_test.dart

+// Copyright (c) 2015, 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 "dart:async";
+import "package:expect/expect.dart";
+
+foo() async {
+  try {
+    print("a");
+    await new Future.value(3);
+    print("b");
+    throw "Error";
+    print("c");
+  } catch (e) {
+    print("d");
+    await new Future.error("Error2");
+  } finally {
+    print("e");
+  }
+  print("f");
+}
+
+main() async {
+  var error = "no error";
+  try {
+    await foo();
+  } catch (e) {
+    error = e;
+  }
+  Expect.equals("Error2", error);
+}
+
+
+