Use packages dart_parser, dart_scanner, and compiler_util.

pkg/compiler/lib/src/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.
 
 library dart2js.scanner.task;
 
 import '../common/tasks.dart' show CompilerTask, Measurer;
 import '../diagnostics/diagnostic_listener.dart' show DiagnosticReporter;
 import '../elements/elements.dart' show CompilationUnitElement, LibraryElement;
 import '../parser/diet_parser_task.dart' show DietParserTask;
 import '../script.dart' show Script;
-import '../tokens/token.dart' show Token;
-import '../tokens/token_constants.dart' as Tokens show COMMENT_TOKEN, EOF_TOKEN;
+import 'package:dart_scanner/dart_scanner.dart'
+    show Scanner, StringScanner, Token, Utf8BytesScanner;
+import 'package:dart_scanner/src/token_constants.dart' as Tokens
+    show COMMENT_TOKEN, EOF_TOKEN;
 import '../tokens/token_map.dart' show TokenMap;
-import 'scanner.dart' show Scanner;
-import 'string_scanner.dart' show StringScanner;
+import '../io/source_file.dart';
 
 class ScannerTask extends CompilerTask {
   final DietParserTask _dietParser;
   final bool _preserveComments;
   final TokenMap _commentMap;
   final DiagnosticReporter reporter;
 
   ScannerTask(this._dietParser, this.reporter, Measurer measurer,
       {bool preserveComments: false, TokenMap commentMap})
       : _preserveComments = preserveComments,
@@ skipping 18 matching lines @@
     }
     scan(compilationUnit);
   }
 
   void scan(CompilationUnitElement compilationUnit) {
     measure(() {
       scanElements(compilationUnit);
     });
   }
 
+  Token scanFile(SourceFile file, {bool includeComments: false}) {
+    Scanner scanner = file is Utf8BytesSourceFile
+        ? new Utf8BytesScanner(file.slowUtf8ZeroTerminatedBytes(),
+            includeComments: includeComments)
+        : new StringScanner(file.slowText(), includeComments: includeComments);
+    return measure(scanner.tokenize);
+  }
+
   void scanElements(CompilationUnitElement compilationUnit) {
     Script script = compilationUnit.script;
-    Token tokens =
-        new Scanner(script.file, includeComments: _preserveComments).tokenize();
+    Token tokens = scanFile(script.file, includeComments: _preserveComments);
     if (_preserveComments) {
       tokens = processAndStripComments(tokens);
     }
     _dietParser.dietParse(compilationUnit, tokens);
   }
 
   /**
    * Returns the tokens for the [source].
    *
    * The [StringScanner] implementation works on strings that end with a '0'
    * value ('\x00'). If [source] does not end with '0', the string is copied
    * before scanning.
    */
   Token tokenize(String source) {
     return measure(() {
-      return new StringScanner.fromString(source, includeComments: false)
-          .tokenize();
+      return new StringScanner(source, includeComments: false).tokenize();
     });
   }
 
   Token processAndStripComments(Token currentToken) {
     Token firstToken = currentToken;
     Token prevToken;
     while (currentToken.kind != Tokens.EOF_TOKEN) {
       if (identical(currentToken.kind, Tokens.COMMENT_TOKEN)) {
         Token firstCommentToken = currentToken;
         while (identical(currentToken.kind, Tokens.COMMENT_TOKEN)) {
           currentToken = currentToken.next;
         }
         _commentMap[currentToken] = firstCommentToken;
         if (prevToken == null) {
           firstToken = currentToken;
         } else {
           prevToken.next = currentToken;
         }
       }
       prevToken = currentToken;
       currentToken = currentToken.next;
     }
     return firstToken;
   }
 }