Patches to support Dart VM patch files in dart2js.

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;
 import '../compiler.dart' show Compiler;
 import '../elements/elements.dart' show CompilationUnitElement, LibraryElement;
 import '../script.dart' show Script;
@@ skipping 58 matching lines @@
    * 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();
     });
   }
 
+  Token tokenizeUnit(CompilationUnitElement unit) {
+    return measureElement(unit, () {
+      Token tokens = new Scanner(
+          unit.script.file, includeComments: _preserveComments).tokenize();
+      if (_preserveComments) {
+        tokens = processAndStripComments(tokens);
+      }
+      return tokens;
+    });
+  }
+
   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;
   }
 }