Switch transformers over to source_span

pkg/polymer/lib/src/build/common.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.
 
 /// Common methods used by transfomers.
 library polymer.src.build.common;
 
 import 'dart:async';
 
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/error.dart';
 import 'package:analyzer/src/generated/parser.dart';
 import 'package:analyzer/src/generated/scanner.dart';
 import 'package:barback/barback.dart';
 import 'package:html5lib/dom.dart' show Document;
 import 'package:html5lib/parser.dart' show HtmlParser;
 import 'package:path/path.dart' as path;
 import 'package:observe/transformer.dart' show ObservableTransformer;
-import 'package:source_maps/span.dart' show Span;
 
 const _ignoredErrors = const [
   'unexpected-dash-after-double-dash-in-comment',
   'unexpected-char-in-comment',
 ];
 
 /// Parses an HTML file [contents] and returns a DOM-like tree. Adds emitted
 /// error/warning to [logger].
 Document _parseHtml(String contents, String sourcePath, TransformLogger logger,
     {bool checkDocType: true, bool showWarnings: true}) {
@@ skipping 88 matching lines @@
         showWarnings: showWarnings);
     });
   }
 
   Future<bool> assetExists(AssetId id, Transform transform) =>
       transform.getInput(id).then((_) => true).catchError((_) => false);
 
   String toString() => 'polymer ($runtimeType)';
 }
 
-/// Gets the appropriate URL to use in a [Span] to produce messages
-/// (e.g. warnings) for users. This will attempt to format the URL in the most
-/// useful way:
+/// Gets the appropriate URL to use in a span to produce messages (e.g.
+/// warnings) for users. This will attempt to format the URL in the most useful
+/// way:
 ///
 /// - If the asset is within the primary package, then use the [id.path],
 ///   the user will know it is a file from their own code.
 /// - If the asset is from another package, then use [assetUrlFor], this will
 ///   likely be a "package:" url to the file in the other package, which is
 ///   enough for users to identify where the error is.
 String spanUrlFor(AssetId id, Transform transform) {
   var primaryId = transform.primaryInput.id;
   bool samePackage = id.package == primaryId.package;
   return samePackage ? id.path
@@ skipping 59 matching lines @@
 bool isCustomTagName(String name) {
   if (name == null || !name.contains('-')) return false;
   return !invalidTagNames.containsKey(name);
 }
 
 /// Regex to split names in the 'attributes' attribute, which supports 'a b c',
 /// 'a,b,c', or even 'a b,c'. This is the same as in `lib/src/declaration.dart`.
 final ATTRIBUTES_REGEX = new RegExp(r'\s|,');
 
 const POLYMER_EXPERIMENTAL_HTML = 'packages/polymer/polymer_experimental.html';