Add NoSourceLocationMarker in old source-info engine.

pkg/compiler/lib/src/io/position_information.dart

 // Copyright (c) 2015, 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.
 
 /// Source information system mapping that attempts a semantic mapping between
 /// offsets of JavaScript code points to offsets of Dart code points.
 
 library dart2js.source_information.position;
 
 import '../common.dart';
@@ skipping 407 matching lines @@
   ///
   ///     foo: function() { return 0; }
   ///                                  ^       // the function end position
   ///                                ^         // the return end position
   ///
   END,
 }
 
 /// Processor that associates [SourceLocation]s from [SourceInformation] on
 /// [js.Node]s with the target offsets in a [SourceMapper].
-class PositionSourceInformationProcessor implements SourceInformationProcessor {
+class PositionSourceInformationProcessor extends SourceInformationProcessor {
   final CodePositionRecorder codePositionRecorder = new CodePositionRecorder();
   CodePositionMap codePositionMap;
   List<TraceListener> traceListeners;
 
   PositionSourceInformationProcessor(SourceMapper sourceMapper,
       [Coverage coverage]) {
     codePositionMap = coverage != null
         ? new CodePositionCoverage(codePositionRecorder, coverage)
         : codePositionRecorder;
     traceListeners = [new PositionTraceListener(sourceMapper)];
@@ skipping 868 matching lines @@
 
   @override
   CodePosition operator [](js.Node node) {
     CodePosition codePosition = codePositions[node];
     if (codePosition == null) {
       coverage.registerNodesWithoutOffset(node);
     }
     return codePosition;
   }
 }