Fix small bugs in dartdoc/apidoc.

utils/apidoc/apidoc.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.
 
 /**
  * This generates the reference documentation for the core libraries that come
  * with dart. It is built on top of dartdoc, which is a general-purpose library
  * for generating docs from any Dart code. This library extends that to include
  * additional information and styling specific to our standard library.
  *
@@ skipping 45 matching lines @@
         break;
 
       default:
         if (arg.startsWith('--exclude-lib=')) {
           excludedLibraries.add(arg.substring('--exclude-lib='.length));
         } else if (arg.startsWith('--include-lib=')) {
           includedLibraries.add(arg.substring('--include-lib='.length));
         } 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;
         }
         break;
     }
   }
 
   final libPath = doc.scriptDir.append('../../sdk/');
 
@@ skipping 378 matching lines @@
    return '''
         <div class="mdn">
         $mdnComment
         <div class="mdn-note"><a href="$mdnUrl">from MDN</a></div>
         </div>
         ''';
   }
 
   String toString() => mdnComment;
 }