First pass at asynchronous input loading in dart2js.

tests/compiler/dart2js/gvn_test.dart

 // Copyright (c) 2011, 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 "package:expect/expect.dart";
 import 'compiler_helper.dart';
 
 const String TEST_ONE = r"""
 void foo(bar) {
   for (int i = 0; i < 1; i++) {
@@ skipping 100 matching lines @@
 
   generated = compile(TEST_TWO, entry: 'foo');
   checkNumberOfMatches(new RegExp("length").allMatches(generated).iterator, 1);
 
   generated = compile(TEST_THREE, entry: 'foo');
   checkNumberOfMatches(new RegExp("number").allMatches(generated).iterator, 1);
 
   generated = compile(TEST_FOUR, entry: 'foo');
   checkNumberOfMatches(new RegExp("shr").allMatches(generated).iterator, 1);
 
-  generated = compileAll(TEST_FIVE);
-  checkNumberOfMatches(
-      new RegExp("get\\\$foo").allMatches(generated).iterator, 1);
+  compileAll(TEST_FIVE).then((generated) {
+    checkNumberOfMatches(
+        new RegExp("get\\\$foo").allMatches(generated).iterator, 1);
+  });
 
-  generated = compileAll(TEST_SIX);
-  Expect.isTrue(generated.contains('for (t1 = a.field === 54; t1;)'));
+  compileAll(TEST_SIX).then((generated) {
+    Expect.isTrue(generated.contains('for (t1 = a.field === 54; t1;)'));
+  });
 
-  generated = compileAll(TEST_SEVEN);
-  Expect.isTrue(generated.contains('for (t1 = a.field === 54; t1;)'));
+  compileAll(TEST_SEVEN).then((generated) {
+    Expect.isTrue(generated.contains('for (t1 = a.field === 54; t1;)'));
+  });
 
-  generated = compileAll(TEST_EIGHT);
-  Expect.isTrue(generated.contains('for (; i < t1; ++i)'));
+  compileAll(TEST_EIGHT).then((generated) {
+    Expect.isTrue(generated.contains('for (; i < t1; ++i)'));
+  });
 }