Fix build

runtime/vm/scanner.h

 // 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.
 //
 // Scanner class for the Dart language. The scanner reads source text
 // and produces a stream of tokens which is used by the parser.
 //
 
 #ifndef VM_SCANNER_H_
 #define VM_SCANNER_H_
@@ skipping 30 matching lines @@
     Token::Kind kind;
     int offset;               // Offset in source string.
     SourcePosition position;  // Text position in source.
     const String* literal;    // Identifier, number or string literal.
   };
 
   class TokenCollector : public ValueObject {
    public:
     TokenCollector() { }
     virtual ~TokenCollector() { }
-    virtual void AddToken(const TokenDescriptor& token);
+    virtual void AddToken(const TokenDescriptor& token) { }
    private:
     DISALLOW_COPY_AND_ASSIGN(TokenCollector);
   };
 
   // Initializes scanner to scan string source.
   Scanner(const String& source, const String& private_key);
   ~Scanner();
 
   // Scans one token at a time.
   void Scan();
@@ skipping 150 matching lines @@
   Zone* zone_;
 
   static KeywordTable keywords_[Token::kNumKeywords];
   static int keywords_char_offset_[kNumLowercaseChars];
 };
 
 
 }  // namespace dart
 
 #endif  // VM_SCANNER_H_