First pass at asynchronous input loading in dart2js.

tests/compiler/dart2js/part_of_test.dart

Index: tests/compiler/dart2js/part_of_test.dart
diff --git a/tests/compiler/dart2js/part_of_test.dart b/tests/compiler/dart2js/part_of_test.dart
index 629c267013c8cc275ca0dc3e36333f8c49772dc7..7477128fe1205113974652e8c483b0cd1807df47 100644
--- a/tests/compiler/dart2js/part_of_test.dart
+++ b/tests/compiler/dart2js/part_of_test.dart
@@ -25,13 +25,14 @@ void main() {
   compiler.registerSource(libraryUri, LIBRARY_SOURCE);
   compiler.registerSource(partUri, PART_SOURCE);
 
-  compiler.libraryLoader.loadLibrary(libraryUri, null, libraryUri);
-  print('errors: ${compiler.errors}');
-  print('warnings: ${compiler.warnings}');
-  Expect.isTrue(compiler.errors.isEmpty);
-  Expect.equals(1, compiler.warnings.length);
-  Expect.equals(MessageKind.LIBRARY_NAME_MISMATCH,
-                compiler.warnings[0].message.kind);
-  Expect.equals('foo',
-      compiler.warnings[0].message.arguments['libraryName'].toString());
+  compiler.libraryLoader.loadLibrary(libraryUri, null, libraryUri).then((_) {
+    print('errors: ${compiler.errors}');
+    print('warnings: ${compiler.warnings}');
+    Expect.isTrue(compiler.errors.isEmpty);
+    Expect.equals(1, compiler.warnings.length);
+    Expect.equals(MessageKind.LIBRARY_NAME_MISMATCH,
+                  compiler.warnings[0].message.kind);
+    Expect.equals('foo',
+        compiler.warnings[0].message.arguments['libraryName'].toString());
+  });
 }