Add NoSourceLocationMarker in old source-info engine.

pkg/compiler/lib/src/io/start_end_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 that maps spans of Dart AST nodes to spans of
 /// JavaScript nodes.
 
 library dart2js.source_information.start_end;
 
 import '../common.dart';
@@ skipping 111 matching lines @@
   }
 }
 
 class StartEndSourceInformationProcessor extends SourceInformationProcessor {
   final SourceMapper sourceMapper;
 
   /// Used to track whether a terminating source location marker has been
   /// registered for the top-most node with source information.
   bool hasRegisteredRoot = false;
 
+  /// The root of the tree. Used to add a [NoSourceLocationMarker] to the start
+  /// of the output.
+  js.Node root;
+
+  /// The root of the current subtree with source information. Used to add
+  /// [NoSourceLocationMarker] after areas with source information.
+  js.Node subRoot;
+
   StartEndSourceInformationProcessor(this.sourceMapper);
 
+  void onStartPosition(js.Node node, int startPosition) {
+    if (root == null) {
+      root = node;
+      sourceMapper.register(
+          node, startPosition, const NoSourceLocationMarker());
+    }
+    if (subRoot == null && node.sourceInformation != null) {
+      subRoot = node;
+    }
+  }
+
   @override
   void onPositions(
       js.Node node, int startPosition, int endPosition, int closingPosition) {
     if (node.sourceInformation != null) {
       StartEndSourceInformation sourceInformation = node.sourceInformation;
       sourceMapper.register(
           node, startPosition, sourceInformation.startPosition);
       if (sourceInformation.endPosition != null) {
         sourceMapper.register(node, endPosition, sourceInformation.endPosition);
       }
       if (!hasRegisteredRoot) {
         sourceMapper.register(node, endPosition, null);
         hasRegisteredRoot = true;
       }
+      if (node == subRoot) {
+        sourceMapper.register(
+            node, endPosition, const NoSourceLocationMarker());
+        subRoot = null;
+      }
     }
   }
 }
 
 /// [SourceInformationBuilder] that generates [PositionSourceInformation].
 class StartEndSourceInformationBuilder extends SourceInformationBuilder {
   final SourceFile sourceFile;
   final String name;
 
   StartEndSourceInformationBuilder(ResolvedAst resolvedAst)
@@ skipping 55 matching lines @@
 
   @override
   SourceInformation buildIf(Node node) => buildGeneric(node);
 
   @override
   SourceInformationBuilder forContext(ResolvedAst resolvedAst,
       {SourceInformation sourceInformation}) {
     return new StartEndSourceInformationBuilder(resolvedAst);
   }
 }