Update charted to 0.4.8 and roll

packages/source_span/lib/src/span.dart

 // Copyright (c) 2014, 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.
 
-library source_span.span;
-
 import 'location.dart';
 import 'span_mixin.dart';
 
 /// A class that describes a segment of source text.
 abstract class SourceSpan implements Comparable<SourceSpan> {
   /// The start location of this span.
   final SourceLocation start;
 
   /// The end location of this span, exclusive.
   final SourceLocation end;
@@ skipping 31 matching lines @@
   int compareTo(SourceSpan other);
 
   /// Formats [message] in a human-friendly way associated with this span.
   ///
   /// [color] may either be a [String], a [bool], or `null`. If it's a string,
   /// it indicates an ANSII terminal color escape that should be used to
   /// highlight the span's text. If it's `true`, it indicates that the text
   /// should be highlighted using the default color. If it's `false` or `null`,
   /// it indicates that the text shouldn't be highlighted.
   String message(String message, {color});
+
+  /// Prints the text associated with this span in a user-friendly way.
+  ///
+  /// This is identical to [message], except that it doesn't print the file
+  /// name, line number, column number, or message. If [length] is 0 and this
+  /// isn't a [SourceSpanWithContext], returns an empty string.
+  ///
+  /// [color] may either be a [String], a [bool], or `null`. If it's a string,
+  /// it indicates an ANSII terminal color escape that should be used to
+  /// highlight the span's text. If it's `true`, it indicates that the text
+  /// should be highlighted using the default color. If it's `false` or `null`,
+  /// it indicates that the text shouldn't be highlighted.
+  String highlight({color});
 }
 
 /// A base class for source spans with [start], [end], and [text] known at
 /// construction time.
 class SourceSpanBase extends SourceSpanMixin {
   final SourceLocation start;
   final SourceLocation end;
   final String text;
 
   SourceSpanBase(this.start, this.end, this.text) {
     if (end.sourceUrl != start.sourceUrl) {
       throw new ArgumentError("Source URLs \"${start.sourceUrl}\" and "
           " \"${end.sourceUrl}\" don't match.");
     } else if (end.offset < start.offset) {
       throw new ArgumentError('End $end must come after start $start.');
     } else if (text.length != start.distance(end)) {
       throw new ArgumentError('Text "$text" must be ${start.distance(end)} '
           'characters long.');
     }
   }
 }