dart2js: add initial support for lookup-maps

tests/compiler/dart2js_extra/lookup_map/live_entry_test.dart

Index: tests/compiler/dart2js_extra/lookup_map/live_entry_test.dart
diff --git a/tests/language/deferred_function_type_lib.dart b/tests/compiler/dart2js_extra/lookup_map/live_entry_test.dart
similarity index 62%
copy from tests/language/deferred_function_type_lib.dart
copy to tests/compiler/dart2js_extra/lookup_map/live_entry_test.dart
index 1f0e610aac59572ef332c77ebb2d2acdac5ab189..aa835a8562b7c1021ee14ee7b06080daf2436829 100644
--- a/tests/language/deferred_function_type_lib.dart
+++ b/tests/compiler/dart2js_extra/lookup_map/live_entry_test.dart
@@ -2,19 +2,12 @@
 // 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 'package:lookup_map/lookup_map.dart';
 import 'package:expect/expect.dart';
-
-class T {
-  A foo(int x) {}
-}
-
 class A{}
-
-typedef A F(int x);
-
-use(x) => x;
-
-runTest() {
-  use(new A());
-  Expect.isTrue(new T().foo is F);
+const map = const LookupMap(const [
+    A, "the-text-for-A",
+]);
+main() {
+  Expect.equals(map[A], 'the-text-for-A');
 }