dart2js: add initial support for lookup-maps

tests/compiler/dart2js_extra/lookup_map/dead_entry_single_nested_pairs_test.dart

Index: tests/compiler/dart2js_extra/lookup_map/dead_entry_single_nested_pairs_test.dart
diff --git a/tests/language/deferred_function_type_lib.dart b/tests/compiler/dart2js_extra/lookup_map/dead_entry_single_nested_pairs_test.dart
similarity index 51%
copy from tests/language/deferred_function_type_lib.dart
copy to tests/compiler/dart2js_extra/lookup_map/dead_entry_single_nested_pairs_test.dart
index 1f0e610aac59572ef332c77ebb2d2acdac5ab189..79446f22c89b1edcda29aca97686e1a16d0b3356 100644
--- a/tests/language/deferred_function_type_lib.dart
+++ b/tests/compiler/dart2js_extra/lookup_map/dead_entry_single_nested_pairs_test.dart
@@ -2,19 +2,15 @@
 // 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{}
+class B{}
+const map = const LookupMap(const [], const [
+    const LookupMap.pair(A, "the-text-for-A"),
+    const LookupMap.pair(B, "the-text-for-B"),
+]);
 
-typedef A F(int x);
-
-use(x) => x;
-
-runTest() {
-  use(new A());
-  Expect.isTrue(new T().foo is F);
+main() {
+  Expect.equals(map[A], "the-text-for-A");
 }