Issue 8742. Preserve leading line comments during java2dart translation.

pkg/analyzer/lib/src/generated/source.dart

 // Copyright (c) 2014, 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.
 
 // This code was auto-generated, is not intended to be edited, and is subject to
 // significant change. Please see the README file for more information.
 
 library engine.source;
 
 import 'java_core.dart';
@@ skipping 178 matching lines @@
    *
    * @param containingSource the source containing the given URI
    * @param containedUri the (possibly relative) URI to be resolved against the containing source
    * @return the source representing the contained URI
    */
   Source resolveUri(Source containingSource, String containedUri) {
     if (containedUri == null || containedUri.isEmpty) {
       return null;
     }
     try {
+      // Force the creation of an escaped URI to deal with spaces, etc.
       return resolveUri2(containingSource, parseUriWithException(containedUri));
     } on URISyntaxException catch (exception) {
       return null;
     }
   }
 
   /**
    * Return an absolute URI that represents the given source.
    *
    * @param source the source to get URI for
@@ skipping 680 matching lines @@
    * @param contents the new contents of the source
    * @return the original cached contents or `null` if none
    */
   String setContents(Source source, String contents) {
     if (contents == null) {
       _stampMap.remove(source);
       return _contentMap.remove(source);
     } else {
       int newStamp = JavaSystem.currentTimeMillis();
       int oldStamp = javaMapPut(_stampMap, source, newStamp);
+      // Occasionally, if this method is called in rapid succession, the timestamps are equal.
+      // Guard against this by artificially incrementing the new timestamp
       if (newStamp == oldStamp) {
         _stampMap[source] = newStamp + 1;
       }
       return javaMapPut(_contentMap, source, contents);
     }
   }
 }