Fixed docgen to work on files without the SDK

pkg/docgen/lib/docgen.dart

 // Copyright (c) 2013, 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.
 
 /**
  * **docgen** is a tool for creating machine readable representations of Dart
  * code metadata, including: classes, members, comments and annotations.
  *
  * docgen is run on a `.dart` file or a directory containing `.dart` files.
  *
@@ skipping 79 matching lines @@
   logger.info('Package Root: ${packageRoot}');
 
   linkResolver = (name) =>
       fixReference(name, _currentLibrary, _currentClass, _currentMember);
 
   return getMirrorSystem(files, packageRoot: packageRoot, parseSdk: parseSdk)
     .then((MirrorSystem mirrorSystem) {
       if (mirrorSystem.libraries.isEmpty) {
         throw new StateError('No library mirrors were created.');
       }
-      _documentLibraries(mirrorSystem.libraries.values,
-          includeSdk: includeSdk, outputToYaml: outputToYaml, append: append);
+      _documentLibraries(mirrorSystem.libraries.values,includeSdk: includeSdk,
+          outputToYaml: outputToYaml, append: append, parseSdk: parseSdk);
 
       return true;
     });
 }
 
 List<String> _listLibraries(List<String> args) {
   if (args.length != 1) throw new UnsupportedError(USAGE);
   var libraries = new List<String>();
   var type = FileSystemEntity.typeSync(args[0]);
 
@@ skipping 81 matching lines @@
         // Currently, a string is thrown when it fails to create a mirror
         // system, and it is not possible to use the stack trace. BUG(#11622)
         // To avoid printing the stack trace.
         exit(1);
       });
 }
 
 /**
  * Creates documentation for filtered libraries.
  */
-void _documentLibraries(List<LibraryMirror> libs,
-    {bool includeSdk: false, bool outputToYaml: true, bool append: false}) {
+void _documentLibraries(List<LibraryMirror> libs, {bool includeSdk: false,
+    bool outputToYaml: true, bool append: false, bool parseSdk: false}) {
   libs.forEach((lib) {
     // Files belonging to the SDK have a uri that begins with 'dart:'.
     if (includeSdk || !lib.uri.toString().startsWith('dart:')) {
       var library = generateLibrary(lib);
       entityMap[library.qualifiedName] = library;
     }
   });
   // After everything is created, do a pass through all classes to make sure no
   // intermediate classes created by mixins are included. 
   entityMap.values.where((e) => e is Class).forEach((c) => c.makeValid());
   // Everything is a subclass of Object, therefore empty the list to avoid a
-  // giant list of subclasses to be printed out. 
-  entityMap['dart.core.Object'].subclasses.clear();
+  // giant list of subclasses to be printed out.
+  if (parseSdk) entityMap['dart.core.Object'].subclasses.clear();
   
   var filteredEntities = entityMap.values.where(_isVisible);
   // Output libraries and classes to file after all information is generated.
   filteredEntities.where((e) => e is Class || e is Library).forEach((output) {
     _writeIndexableToFile(output, outputToYaml);
   });
   // Outputs a text file with a list of libraries available after creating all
   // the libraries. This will help the viewer know what libraries are available
   // to read in.
   _writeToFile(filteredEntities.where((e) => e is Library)
@@ skipping 709 matching lines @@
   String outer;
   List<Type> inner;
   
   Type(this.outer, this.inner);
   
   Map toMap() => {
     'outer': outer,
     'inner': new List.from(inner.map((e) => e.toMap()))
   };
 }