Fix small bugs in dartdoc/apidoc.

utils/apidoc/apidoc.dart

Index: utils/apidoc/apidoc.dart
diff --git a/utils/apidoc/apidoc.dart b/utils/apidoc/apidoc.dart
index bba8136b0f08f3367870457dc8ecfdd045beaa39..bf6324f3ec38cccd1aaaf45f796d9159ce105dd8 100644
--- a/utils/apidoc/apidoc.dart
+++ b/utils/apidoc/apidoc.dart
@@ -63,7 +63,7 @@ void main() {
         } else if (arg.startsWith('--out=')) {
           outputDir = new Path(arg.substring('--out='.length));
         } else if (arg.startsWith('--pkg=')) {
-          pkgPath = arg.substring('--pkg='.length);
+          pkgPath = new Path(arg.substring('--pkg='.length));
         } else {
           print('Unknown option: $arg');
           return;