Add new core ("dart:") libraries to frog so that apidoc can find them.

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.
 
 /**
  * Generates the complete set of corelib reference documentation.
  */
 #library('apidoc');
 
 #import('dart:json');
@@ skipping 17 matching lines @@
 
   print('Cross-referencing dart:dom and dart:html...');
   HtmlDiff.initialize();
   _diff = new HtmlDiff();
   _diff.run();
   world.reset();
 
   // TODO(rnystrom): Cram in the the IO libraries. This is hackish right now.
   // We should probably move corelib stuff completely out of dartdoc and have it
   // all here.
-  world.getOrAddLibrary('io_libs.dart');
+  world.getOrAddLibrary('dart:io');
 
   print('Generating docs...');
   final apidoc = new Apidoc(mdn);
   apidoc.document('html');
 }
 
 class Apidoc extends doc.Dartdoc {
   /** Big ball of JSON containing the scraped MDN documentation. */
   final Map mdn;
 
@@ skipping 334 matching lines @@
       return
           '''
           <p class="correspond">This corresponds to $domTypesText in the
           ${a("dom.html", "dart:dom")} library.</p>
           ''';
     }
 
     return '';
   }
 }