Support unmapped areas in source maps.

pkg/source_maps/lib/builder.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.
 
 /// Contains a builder object useful for creating source maps programatically.
 library source_maps.builder;
 
 // TODO(sigmund): add a builder for multi-section mappings.
 
 import 'dart:collection';
@@ skipping 57 matching lines @@
         line = nextLine;
         column = 0;
         first = true;
       }
 
       if (!first) buff.write(',');
       first = false;
       column = _append(buff, column, entry.target.column);
 
       // Encoding can be just the column offset if there is no source
-      // information, or if two consecutive mappings share exactly the same
-      // source information.
+      // information.
       var source = entry.source;
       if (source == null) continue;
       var newUrlId = _indexOf(_urls, source.sourceUrl);
-      if (newUrlId == srcUrlId && source.line == srcLine
-          && source.column == srcColumn && entry.identifierName == null) {
-        continue;
-      }
 
       srcUrlId = _append(buff, srcUrlId, newUrlId);
       srcLine = _append(buff, srcLine, source.line);
       srcColumn = _append(buff, srcColumn, source.column);
 
       if (entry.identifierName == null) continue;
       srcNameId = _append(buff, srcNameId,
           _indexOf(_names, entry.identifierName));
     }
 
@@ skipping 48 matching lines @@
   /// because source map files are encoded by printing each mapping in order as
   /// they appear in the target file.
   int compareTo(Entry other) {
     int res = target.compareTo(other.target);
     if (res != 0) return res;
     res = source.sourceUrl.compareTo(other.source.sourceUrl);
     if (res != 0) return res;
     return source.compareTo(other.source);
   }
 }