Switch transformers over to source_span

pkg/polymer/lib/src/build/linter.dart

 // Copyright (c) 2013, 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.
 
 /// Logic to validate that developers are correctly using Polymer constructs.
 /// This is mainly used to produce warnings for feedback in the editor.
 library polymer.src.build.linter;
 
 import 'dart:async';
 
 import 'package:barback/barback.dart';
 import 'package:code_transformers/assets.dart';
 import 'package:html5lib/dom.dart';
 import 'package:html5lib/dom_parsing.dart';
-import 'package:source_maps/span.dart';
+import 'package:source_span/source_span.dart';
 
 import 'common.dart';
 import 'utils.dart';
 
 /// A linter that checks for common Polymer errors and produces warnings to
 /// show on the editor or the command line. Leaves sources unchanged, but
 /// creates a new asset containing all the warnings.
 class Linter extends Transformer with PolymerTransformer {
   final TransformOptions options;
 
@@ skipping 97 matching lines @@
 
 
 /// Information needed about other polymer-element tags in order to validate
 /// how they are used and extended.
 ///
 /// Note: these are only created for polymer-element, because pure custom
 /// elements don't have a declarative form.
 class _ElementSummary {
   final String tagName;
   final String extendsTag;
-  final Span span;
+  final SourceSpan span;
 
   _ElementSummary extendsType;
   bool hasConflict = false;
 
   String get baseExtendsTag {
     if (extendsType != null) return extendsType.baseExtendsTag;
     if (extendsTag != null && !extendsTag.contains('-')) return extendsTag;
     return null;
   }
 
@@ skipping 306 matching lines @@
     '\'<script type="application/dart">export "package:polymer/init.dart";'
     '</script>\' or add your own script tag and call that function. '
     'Make sure the script tag is placed after all HTML imports.';
 
 const String NO_DART_SCRIPT_AND_EXPERIMENTAL =
     'The experimental bootstrap feature doesn\'t support script tags on '
     'the main document (for now).';
 
 const List<String> INTERNALLY_DEFINED_ELEMENTS = 
     const ['auto-binding-dart', 'polymer-element'];