First pass at asynchronous input loading in dart2js.

tests/compiler/dart2js/deprecated_features_test.dart

 // Copyright (c) 2012, 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.
 
 // Test that deprecated language features are diagnosed correctly.
 
 import "package:expect/expect.dart";
 import 'dart:async';
 
 import '../../../sdk/lib/_internal/compiler/compiler.dart';
@@ skipping 15 matching lines @@
     }
   }
 
   Future<String> provider(Uri uri) {
     if (uri.scheme != "main") return dummy.provider(uri);
     String source = TEST_SOURCE[uri.path];
     Expect.isNotNull(source);
     return new Future<String>.value(source);
   }
 
-  String code = deprecatedFutureValue(
-      compile(new Uri(scheme: 'main'),
-              new Uri(scheme: 'lib', path: '/'),
-              new Uri(scheme: 'package', path: '/'),
-              provider, handler));
-  if (code == null) {
-    throw 'Compilation failed: ${messages}';
-  }
-  Expect.stringEquals(
-      // This string is composed of lines of the following format:
-      //
-      // offset<source>:path:kind: message
-      //
-      // "offset" is the character offset from the beginning of TEST_SOURCE.
-      // "source" is the substring of TEST_SOURCE that the compiler is
-      // indicating as erroneous.
-      // "path" is the URI path.
-      // "kind" is the result of calling toString on a [Diagnostic] object.
-      // "message" is the expected message as a [String].  This is a
-      // short-term solution and should eventually changed to include
-      // a symbolic reference to a MessageKind.
-      "15<part 'part.dart';>::${deprecatedMessage('missing part-of tag')}\n"
-      "0<>:/part.dart:info: Note: This file has no part-of tag, but it is being"
-      " used as a part.\n"
-      "53<()>::${deprecatedMessage('getter parameters')}\n",
-      messages.toString());
+  compile(new Uri(scheme: 'main'),
+          new Uri(scheme: 'lib', path: '/'),
+          new Uri(scheme: 'package', path: '/'),
+          provider, handler).then((code) {
+    if (code == null) {
+      throw 'Compilation failed: ${messages}';
+    }
+    Expect.stringEquals(
+        // This string is composed of lines of the following format:
+        //
+        // offset<source>:path:kind: message
+        //
+        // "offset" is the character offset from the beginning of TEST_SOURCE.
+        // "source" is the substring of TEST_SOURCE that the compiler is
+        // indicating as erroneous.
+        // "path" is the URI path.
+        // "kind" is the result of calling toString on a [Diagnostic] object.
+        // "message" is the expected message as a [String].  This is a
+        // short-term solution and should eventually changed to include
+        // a symbolic reference to a MessageKind.
+        "15<part 'part.dart';>::${deprecatedMessage('missing part-of tag')}\n"
+        "0<>:/part.dart:info: Note: This file has no part-of tag, but it is"
+        " being used as a part.\n"
+        "53<()>::${deprecatedMessage('getter parameters')}\n",
+        messages.toString());
+  });
 }
 
 deprecatedMessage(feature) {
   return
     "warning: Warning: Deprecated language feature, $feature"
     ", will be removed in a future Dart milestone.";
 }
 
 const Map<String, String> TEST_SOURCE =
   const <String, String>{ '': """
 library test;
 
 part 'part.dart';
 
 class Foo {
   get x() => null;
 }
 
 main() {
   var a = new Foo();
 }
 """,
     // TODO(ahe): Why isn't this 'part.dart'? Why the leading slash?
     '/part.dart': '',
   };