Use source_span rather than source_maps in csslib.

pkg/csslib/lib/src/tree_base.dart

 // Copyright (c) 2012, 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.
 
 part of csslib.visitor;
 
 /**
  * The base type for all nodes in a CSS abstract syntax tree.
  */
 abstract class TreeNode {
   /** The source code this [TreeNode] represents. */
-  final Span span;
+  final SourceSpan span;
 
   TreeNode(this.span);
 
   TreeNode clone();
 
   /** Classic double-dispatch visitor for implementing passes. */
   void visit(VisitorBase visitor);
 
   /** A multiline string showing the node and its children. */
   String toDebugString() {
     var to = new TreeOutput();
     var tp = new _TreePrinter(to, true);
     this.visit(tp);
     return to.buf.toString();
   }
 }
 
 /** The base type for expressions. */
 abstract class Expression extends TreeNode {
-  Expression(Span span): super(span);
+  Expression(SourceSpan span): super(span);
 }
 
 /** Simple class to provide a textual dump of trees for debugging. */
 class TreeOutput {
   int depth = 0;
   final StringBuffer buf = new StringBuffer();
   VisitorBase printer;
 
   void write(String s) {
     for (int i=0; i < depth; i++) {
       buf.write(' ');
     }
     buf.write(s);
   }
 
   void writeln(String s) {
     write(s);
     buf.write('\n');
   }
 
   void heading(String name, [span]) {
     write(name);
     if (span != null) {
-      buf.write('  (${span.getLocationMessage('')})');
+      buf.write('  (${span.message('')})');
     }
     buf.write('\n');
   }
 
   String toValue(value) {
     if (value == null) return 'null';
     else if (value is Identifier) return value.name;
     else return value.toString();
   }
 
@@ skipping 21 matching lines @@
           writeln('null');
         }
       }
       depth -= 1;
       writeln(']');
     }
   }
 
   String toString() => buf.toString();
 }