Remove >>> and >>>= from scanner.

dart/lib/compiler/implementation/scanner/scanner.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.
 
 abstract class Scanner {
   Token tokenize();
 }
 
 /**
  * Common base class for a Dart scanner.
@@ skipping 413 matching lines @@
     // > >= >> >>= >>> >>>=
     next = advance();
     if ($EQ === next) {
       appendPrecedenceToken(GT_EQ_INFO);
       return advance();
     } else if ($GT === next) {
       next = advance();
       if ($EQ === next) {
         appendPrecedenceToken(GT_GT_EQ_INFO);
         return advance();
-      } else if ($GT === next) {
-        next = advance();
-        if (next === $EQ) {
-          appendPrecedenceToken(GT_GT_GT_EQ_INFO);
-          return advance();
-        } else {
-          appendGtGtGt(GT_GT_GT_INFO, ">>>");
-          return next;
-        }
       } else {
         appendGtGt(GT_GT_INFO, ">>");
         return next;
       }
     } else {
       appendGt(GT_INFO, ">");
       return next;
     }
   }
 
@@ skipping 419 matching lines @@
       next = advance();
     }
     return error(const SourceString("unterminated string literal"));
   }
 
   int error(SourceString message) {
     appendByteStringToken(BAD_INPUT_INFO, message);
     return advance(); // Ensure progress.
   }
 }