Switch transformers over to source_span

pkg/third_party/html5lib/lib/src/tokenizer.dart

 library tokenizer;
 
 import 'dart:collection';
 import 'package:html5lib/parser.dart' show HtmlParser;
-import 'package:source_maps/span.dart' show Span, FileSpan;
 import 'constants.dart';
 import 'inputstream.dart';
 import 'token.dart';
 import 'utils.dart';
 
 // Group entities by their first character, for faster lookups
 
 // TODO(jmesserly): we could use a better data structure here like a trie, if
 // we had it implemented in Dart.
 Map<String, List<String>> entitiesByFirstChar = (() {
@@ skipping 134 matching lines @@
     temporaryBuffer = null;
     _attributes = null;
     _attributeNames = null;
     state = dataState;
   }
 
   /// Adds a token to the queue. Sets the span if needed.
   void _addToken(Token token) {
     if (generateSpans && token.span == null) {
       int offset = stream.position;
-      token.span = new FileSpan(stream.fileInfo, _lastOffset, offset);
+      token.span = stream.fileInfo.span(_lastOffset, offset);
       if (token is! ParseErrorToken) {
         _lastOffset = offset;
       }
     }
     tokenQueue.add(token);
   }
 
   /// This function returns either U+FFFD or the character based on the
   /// decimal or hexadecimal representation. It also discards ";" if present.
   /// If not present it will add a [ParseErrorToken].
@@ skipping 1707 matching lines @@
     }
 
     if (data.length > 0) {
       _addToken(new CharactersToken(data.join()));
     }
     state = dataState;
     return true;
   }
 }