remove docgen source and targets from build

pkg/docgen/lib/src/models/closure.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.closure;
-
-import '../exports/source_mirrors.dart';
-
-import 'doc_gen_type.dart';
-import 'indexable.dart';
-import 'mirror_based.dart';
-import 'model_helpers.dart';
-import 'parameter.dart';
-
-/// A class containing the properties of a function to be called (used in our
-/// case specifically to illustrate evidence of the type of function for a
-/// parameter).
-class Closure extends MirrorBased<FunctionTypeMirror> {
-
-  /// Parameters for this method.
-  final Map<String, Parameter> parameters;
-  final DocGenType returnType;
-  final FunctionTypeMirror mirror;
-
-  Closure(FunctionTypeMirror mirror, Indexable owner)
-    : returnType = new DocGenType(mirror.returnType, owner.owningLibrary),
-      parameters = createParameters(mirror.parameters, owner),
-      mirror = mirror;
-
-  /// Generates a map describing the [Method] object.
-  Map toMap() => {
-    'return': [returnType.toMap()],
-    'parameters': recurseMap(parameters),
-  };
-}