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sdk/lib/_internal/compiler/implementation/scanner/scanner_task.dart

 // Copyright (c) 2012, 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.
 
 part of scanner;
 
 class ScannerTask extends CompilerTask {
   ScannerTask(Compiler compiler) : super(compiler);
   String get name => 'Scanner';
 
@@ skipping 10 matching lines @@
   }
 
   void scan(CompilationUnitElement compilationUnit) {
     measure(() {
       scanElements(compilationUnit);
     });
   }
 
   void scanElements(CompilationUnitElement compilationUnit) {
     Script script = compilationUnit.script;
-    Token tokens = new StringScanner(script.text).tokenize();
+    Token tokens = new StringScanner(script.text,
+        includeComments: compiler.preserveComments).tokenize();
+    if (compiler.preserveComments) {
+      tokens = compiler.processAndStripComments(tokens);
+    }
     compiler.dietParser.dietParse(compilationUnit, tokens);
   }
 }
 
 class DietParserTask extends CompilerTask {
   DietParserTask(Compiler compiler) : super(compiler);
   final String name = 'Diet Parser';
 
   dietParse(CompilationUnitElement compilationUnit, Token tokens) {
     measure(() {
       Function idGenerator = compiler.getNextFreeClassId;
       ElementListener listener =
           new ElementListener(compiler, compilationUnit, idGenerator);
       PartialParser parser = new PartialParser(listener);
       parser.parseUnit(tokens);
     });
   }
 }