First pass at asynchronous input loading in dart2js.

tests/compiler/dart2js/deferred_load_graph_segmentation_test.dart

Index: tests/compiler/dart2js/deferred_load_graph_segmentation_test.dart
diff --git a/tests/compiler/dart2js/deferred_load_graph_segmentation_test.dart b/tests/compiler/dart2js/deferred_load_graph_segmentation_test.dart
index eec688ab4c5aff7b4884562daadf5f323747f631..bc8c8ca1f51ceece547a6b93f8845fc429623c83 100644
--- a/tests/compiler/dart2js/deferred_load_graph_segmentation_test.dart
+++ b/tests/compiler/dart2js/deferred_load_graph_segmentation_test.dart
@@ -27,26 +27,27 @@ void main() {
                                    libraryRoot,
                                    packageRoot,
                                    ['--analyze-only']);
-  compiler.run(Uri.parse('memory:main.dart'));
-  var main = compiler.mainApp.find(dart2js.Compiler.MAIN);
-  Expect.isNotNull(main, 'Could not find "main"');
-  compiler.deferredLoadTask.onResolutionComplete(main);
+  compiler.run(Uri.parse('memory:main.dart')).then((_) {
+    var main = compiler.mainApp.find(dart2js.Compiler.MAIN);
+    Expect.isNotNull(main, 'Could not find "main"');
+    compiler.deferredLoadTask.onResolutionComplete(main);
 
-  var deferredClasses =
-      compiler.deferredLoadTask.allDeferredElements.where((e) => e.isClass())
-      .toSet();
+    var deferredClasses =
+        compiler.deferredLoadTask.allDeferredElements.where((e) => e.isClass())
+        .toSet();
 
-  var dateTime =
-      deferredClasses
-          .where((e) => e.name.slowToString() == 'DateTime').single;
+    var dateTime =
+        deferredClasses
+            .where((e) => e.name.slowToString() == 'DateTime').single;
 
-  var myClass =
-      deferredClasses.where((e) => e.name.slowToString() == 'MyClass').single;
+    var myClass =
+        deferredClasses.where((e) => e.name.slowToString() == 'MyClass').single;
 
-  var deferredLibrary = compiler.libraries['memory:deferred.dart'];
+    var deferredLibrary = compiler.libraries['memory:deferred.dart'];
 
-  Expect.equals(deferredLibrary, myClass.getLibrary());
-  Expect.equals(compiler.coreLibrary, dateTime.declaration.getLibrary());
+    Expect.equals(deferredLibrary, myClass.getLibrary());
+    Expect.equals(compiler.coreLibrary, dateTime.declaration.getLibrary());
+  });
 }
 
 const Map MEMORY_SOURCE_FILES = const {