Convert raw strings in compiler

lib/compiler/implementation/dart_backend/renamer.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.
 
 Function get _compareNodes =>
     compareBy((n) => n.getBeginToken().charOffset);
 
 typedef String _Renamer(Renamable renamable);
 abstract class Renamable {
   const int RENAMABLE_TYPE_ELEMENT = 1; 
@@ skipping 240 matching lines @@
   String newName = originalName;
   while (isForbidden(newName)) {
     newName = 'p_$newName';
   }
   return newName;
 }
 
 /** Always tries to generate the most compact identifier. */
 class MinifyingGenerator {
   static const String firstCharAlphabet =
-      @'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz';
+      r'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz';
   static const String otherCharsAlphabet =
-      @'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789_$';
+      r'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789_$';
   int nextIdIndex;
 
   MinifyingGenerator() : nextIdIndex = 0;
 
   String generate(bool isForbidden(String name)) {
     String newName;
     do {
       newName = getNextId();
     } while(isForbidden(newName));
     return newName;
@@ skipping 14 matching lines @@
     index ~/= firstCharAlphabet.length;
     int length = otherCharsAlphabet.length;
     while (index >= length) {
       resultBuilder.add(otherCharsAlphabet[index % length]);
       index ~/= length;
     }
     resultBuilder.add(otherCharsAlphabet[index]);
     return resultBuilder.toString();
   }
 }