Split parser/listener.dart, parser/class_element_listener.dart and tokens/token.dart into smaller l…

pkg/compiler/lib/src/scanner/string_scanner.dart

 // Copyright (c) 2011, 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.string;
 
 import '../io/source_file.dart' show
     SourceFile;
+import '../tokens/precedence.dart' show
+    PrecedenceInfo;
 import '../tokens/token.dart' show
     PrecedenceInfo,
     StringToken,
     Token;
 
 import 'array_based_scanner.dart' show
     ArrayBasedScanner;
 
 
 /**
@@ skipping 39 matching lines @@
 
   void appendSubstringToken(PrecedenceInfo info, int start,
                             bool asciiOnly, [int extraOffset = 0]) {
     tail.next = new StringToken.fromSubstring(info, string, start,
         scanOffset + extraOffset, tokenStart, canonicalize: true);
     tail = tail.next;
   }
 
   bool atEndOfFile() => scanOffset >= string.length - 1;
 }