Switch transformers over to source_span

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

Index: pkg/polymer/lib/src/build/linter.dart
diff --git a/pkg/polymer/lib/src/build/linter.dart b/pkg/polymer/lib/src/build/linter.dart
index a48badbf2fa554e64cdee41f26ddfda8159b6288..714e50e743b706d0cf339ba6f1d2bb312f454ada 100644
--- a/pkg/polymer/lib/src/build/linter.dart
+++ b/pkg/polymer/lib/src/build/linter.dart
@@ -12,7 +12,7 @@ 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';
@@ -130,7 +130,7 @@ class Linter extends Transformer with PolymerTransformer {
 class _ElementSummary {
   final String tagName;
   final String extendsTag;
-  final Span span;
+  final SourceSpan span;
 
   _ElementSummary extendsType;
   bool hasConflict = false;