Revert "Change dart:io Platform.script to return a Uri."

pkg/third_party/html5lib/test/support.dart

 /** Support code for the tests in this directory. */
 library support;
 
 import 'dart:async';
 import 'dart:io';
 import 'dart:collection';
 import 'package:path/path.dart' as path;
 import 'package:html5lib/src/treebuilder.dart';
 import 'package:html5lib/dom.dart';
 import 'package:html5lib/dom_parsing.dart';
 
 typedef TreeBuilder TreeBuilderFactory(bool namespaceHTMLElements);
 
 Map _treeTypes;
 Map<String, TreeBuilderFactory> get treeTypes {
   if (_treeTypes == null) {
     // TODO(jmesserly): add DOM here once it's implemented
     _treeTypes = { "simpletree": (useNs) => new TreeBuilder(useNs) };
   }
   return _treeTypes;
 }
 
-final testDataDir = Platform.script.resolve('data').toFilePath();
+final testDataDir = path.join(path.dirname(Platform.script), 'data');
 
 Iterable<String> getDataFiles(String subdirectory) {
   var dir = new Directory(path.join(testDataDir, subdirectory));
   return dir.listSync().where((f) => f is File).map((f) => f.path);
 }
 
 // TODO(jmesserly): make this class simpler. We could probably split on
 // "\n#" instead of newline and remove a lot of code.
 class TestData extends IterableBase<Map> {
   final String _text;
@@ skipping 125 matching lines @@
           key = "${attr.prefix} ${attr.name}";
         }
         _newline();
         _str.write('$key="$v"');
       }
       indent -= 2;
     }
     visitChildren(node);
   }
 }