remove docgen source and targets from build

pkg/docgen/lib/src/models/variable.dart

-// Copyright (c) 2014, 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.
-
-library docgen.models.variable;
-
-import '../exports/source_mirrors.dart';
-
-import '../library_helpers.dart';
-
-import 'class.dart';
-import 'doc_gen_type.dart';
-import 'dummy_mirror.dart';
-import 'indexable.dart';
-import 'owned_indexable.dart';
-
-
-/// A class containing properties of a Dart variable.
-class Variable extends OwnedIndexable<VariableMirror> {
-  final bool isFinal;
-  final bool isStatic;
-  final bool isConst;
-  final DocGenType type;
-  final String name;
-
-  factory Variable(String name, VariableMirror mirror, Indexable owner) {
-    var variable = getDocgenObject(mirror, owner);
-    if (variable is DummyMirror) {
-      return new Variable._(name, mirror, owner);
-    }
-    return variable;
-  }
-
-  Variable._(this.name, VariableMirror mirror, Indexable owner)
-      : isFinal = mirror.isFinal,
-        isStatic = mirror.isStatic,
-        isConst = mirror.isConst,
-        type = new DocGenType(mirror.type, owner.owningLibrary),
-        super(mirror, owner);
-
-  /// Generates a map describing the [Variable] object.
-  Map toMap() => {
-    'name': name,
-    'qualifiedName': qualifiedName,
-    'comment': comment,
-    'final': isFinal,
-    'static': isStatic,
-    'constant': isConst,
-    'type': new List.filled(1, type.toMap()),
-    'annotations': annotations.map((a) => a.toMap()).toList()
-  };
-
-  String get typeName => 'property';
-
-  String get comment {
-    if (commentField != null) return commentField;
-    if (owner is Class) {
-      (owner as Class).ensureComments();
-    }
-    return super.comment;
-  }
-
-  bool isValidMirror(DeclarationMirror mirror) => mirror is VariableMirror;
-}