Add LibraryDependencyMirror.isDeferred.

tests/lib/mirrors/library_imports_deferred_test.dart

+// Copyright (c) 2015, 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.
+
+library test.library_imports_deferred;
+
+import 'dart:mirrors';
+import 'package:expect/expect.dart';
+import 'stringify.dart';
+
+import 'dart:collection' as eagercollection;
+import 'dart:collection' deferred as lazycollection;
+
+test(MirrorSystem mirrors) {
+  LibraryMirror thisLibrary =
+      mirrors.findLibrary(#test.library_imports_deferred);
+  LibraryMirror collection  =
+      mirrors.findLibrary(#dart.collection);
+
+  var importsOfCollection = thisLibrary.libraryDependencies.where(
+      (dep) => dep.targetLibrary == collection).toList();
+  Expect.equals(2, importsOfCollection.length);
+  Expect.notEquals(importsOfCollection[0].isDeferred,
+                   importsOfCollection[1].isDeferred);  // One deferred, one not.
+
+  // Only collection is defer-imported.
+  LibraryDependencyMirror dep =
+      thisLibrary.libraryDependencies.singleWhere((dep) => dep.isDeferred);
+  Expect.equals(collection, dep.targetLibrary);
+
+  Expect.stringEquals(
+      'import dart.collection as eagercollection\n'
+      'import dart.collection deferred as lazycollection\n'
+      ' hide loadLibrary\n'
+      'import dart.core\n'
+      'import dart.mirrors\n'
+      'import expect\n'
+      'import test.stringify\n',
+      stringifyDependencies(thisLibrary));
+}
+
+main() {
+  test(currentMirrorSystem());
+}