Allow DirectoryDescriptor.load to load a file next to a directory.

pkg/scheduled_test/lib/src/descriptor/async_descriptor.dart

Index: pkg/scheduled_test/lib/src/descriptor/async_descriptor.dart
diff --git a/pkg/scheduled_test/lib/src/descriptor/async_descriptor.dart b/pkg/scheduled_test/lib/src/descriptor/async_descriptor.dart
index 79092dc6d70242e63f21207567b243b53877e062..e46e17bc8505ca01b9629d4587b748a8afd22121 100644
--- a/pkg/scheduled_test/lib/src/descriptor/async_descriptor.dart
+++ b/pkg/scheduled_test/lib/src/descriptor/async_descriptor.dart
@@ -33,11 +33,5 @@ class AsyncDescriptor extends Descriptor {
   Future validateNow([String parent]) =>
     future.then((entry) => entry.validateNow(parent));
 
-  Stream<List<int>> load(String path) => errorStream("AsyncDescriptors don't "
-      "support load().");
-
-  Stream<List<int>> read() => errorStream("AsyncDescriptors don't support "
-      "read().");
-
   String describe() => "async descriptor";
 }