Make VirtualDirectory redirect if the directory-path does not end with a tailing slash.

pkg/http_server/test/virtual_directory_test.dart

Index: pkg/http_server/test/virtual_directory_test.dart
diff --git a/pkg/http_server/test/virtual_directory_test.dart b/pkg/http_server/test/virtual_directory_test.dart
index 97ec5ca8984f8154905321294289656a011cfc6e..6583e592dc1c60d00692f06346032bfe89fdbde6 100644
--- a/pkg/http_server/test/virtual_directory_test.dart
+++ b/pkg/http_server/test/virtual_directory_test.dart
@@ -231,6 +231,20 @@ void main() {
       });
 
       _testVirDir('index-2', (server, dir) {
+        new Directory('${dir.path}/dir').createSync();
+        var virDir = new VirtualDirectory(dir.path);
+        virDir.allowDirectoryListing = true;
+        virDir.directoryHandler = (dir2, request) {
+          fail('not expected');
+        };
+        virDir.serve(server);
+        return getStatusCode(server.port, '/dir', followRedirects: false)
+          .then((result) {
+            expect(result, 301);
+          });
+      });
+
+      _testVirDir('index-3', (server, dir) {
         new File('${dir.path}/dir/index.html')
             ..createSync(recursive: true)
             ..writeAsStringSync('index file');
@@ -247,6 +261,24 @@ void main() {
             expect(result, 'index file');
           });
       });
+
+      _testVirDir('index-4', (server, dir) {
+        new File('${dir.path}/dir/index.html')
+            ..createSync(recursive: true)
+            ..writeAsStringSync('index file');
+        var virDir = new VirtualDirectory(dir.path);
+        virDir.allowDirectoryListing = true;
+        virDir.directoryHandler = (dir2, request) {
+          // Redirect directory-requests to index.html files.
+          var indexUri = new Uri.file(dir2.path).resolve('index.html');
+          virDir.serveFile(new File(indexUri.toFilePath()), request);
+        };
+        virDir.serve(server);
+        return getAsString(server.port, '/dir/')
+          .then((result) {
+            expect(result, 'index file');
+          });
+      });
     });
   });