Add SourceInformationFactory.

pkg/compiler/lib/src/js/js.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.
 
 library js;
 
 import 'package:js_ast/js_ast.dart';
 export 'package:js_ast/js_ast.dart';
 
+import '../helpers/helpers.dart';
 import '../io/code_output.dart' show CodeBuffer;
 import '../io/source_information.dart' show SourceInformation;
 import '../js_emitter/js_emitter.dart' show USE_NEW_EMITTER;
 import '../dart2jslib.dart' as leg;
 import '../util/util.dart' show NO_LOCATION_SPANNABLE;
 import '../dump_info.dart' show DumpInfoTask;
 
 
 CodeBuffer prettyPrint(Node node, leg.Compiler compiler,
                        {DumpInfoTask monitor,
@@ skipping 11 matching lines @@
 
 class Dart2JSJavaScriptPrintingContext implements JavaScriptPrintingContext {
   final leg.Compiler compiler;
   final DumpInfoTask monitor;
   final CodeBuffer outBuffer = new CodeBuffer();
   Node rootNode;
 
   Dart2JSJavaScriptPrintingContext(leg.Compiler this.compiler,
       DumpInfoTask this.monitor);
 
+  @override
   void error(String message) {
     compiler.internalError(NO_LOCATION_SPANNABLE, message);
   }
 
+  @override
   void emit(String string) {
     outBuffer.add(string);
   }
 
+  @override
   void enterNode(Node node, int startPosition) {
     SourceInformation sourceInformation = node.sourceInformation;
     if (sourceInformation != null) {
       if (rootNode == null) {
         rootNode = node;
       }
       if (sourceInformation.startPosition != null) {
         outBuffer.addSourceLocation(
             startPosition, sourceInformation.startPosition);
       }
     }
   }
 
   void exitNode(Node node,
                 int startPosition,
                 int endPosition,
                 int closingPosition) {
     SourceInformation sourceInformation = node.sourceInformation;
     if (sourceInformation != null) {
+      if (closingPosition != null &&
+          sourceInformation.closingPosition != null) {
+        outBuffer.addSourceLocation(
+            closingPosition, sourceInformation.closingPosition);
+      }
       if (sourceInformation.endPosition != null) {
         outBuffer.addSourceLocation(endPosition, sourceInformation.endPosition);
       }
       if (rootNode == node) {
         outBuffer.addSourceLocation(endPosition, null);
         rootNode = null;
       }
     }
     if (monitor != null) {
       monitor.recordAstSize(node, endPosition - startPosition);
     }
   }
 }