Generate docgen file names with hyphens in their names instead of colons

pkg/docgen/lib/src/generator.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.generator;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:convert';
 import 'dart:io';
@@ skipping 229 matching lines @@
   _writeToFile(buffer.toString(), 'index.txt');
 
   var index = new SplayTreeMap.fromIterable(filteredEntities,
       key: (e) => e.qualifiedName, value: (e) => e.typeName);
 
   _writeToFile(encoder.convert(index), 'index.json');
 }
 
 /// Helper method to serialize the given Indexable out to a file.
 void _writeIndexableToFile(Indexable result, JsonEncoder encoder) {
-  var outputFile = result.qualifiedName + '.json';
+  var outputFile = result.fileName + '.json';
   var output = encoder.convert(result.toMap());
   _writeToFile(output, outputFile);
 }
 
 /// Set the location of the ouput directory, and ensure that the location is
 /// available on the file system.
 void _ensureOutputDirectory(String outputDirectory) {
   _outputDirectory = outputDirectory;
   var dir = new Directory(_outputDirectory);
   if (dir.existsSync()) dir.deleteSync(recursive: true);
@@ skipping 213 matching lines @@
   * [Samples](http://www.dartlang.org/samples/)
   * [A Tour of the Dart Libraries](http://www.dartlang.org/docs/dart-up-and-running/contents/ch03.html)
 
 This API reference is automatically generated from the source code in the
 [Dart project](https://code.google.com/p/dart/).
 If you'd like to contribute to this documentation, see
 [Contributing](https://code.google.com/p/dart/wiki/Contributing)
 and
 [Writing API Documentation](https://code.google.com/p/dart/wiki/WritingApiDocumentation).
 """;