Fix an ASSERT in the scanner

src/scanner.h

Index: src/scanner.h
===================================================================
--- src/scanner.h	(revision 2728)
+++ src/scanner.h	(working copy)
@@ -212,6 +212,8 @@
   static unibrow::Predicate<unibrow::LineTerminator, 128> kIsLineTerminator;
   static unibrow::Predicate<unibrow::WhiteSpace, 128> kIsWhiteSpace;
 
+  static const int kCharacterLookaheadBufferSize = 1;
+
  private:
   CharacterStreamUTF16Buffer char_stream_buffer_;
   TwoByteStringUTF16Buffer two_byte_string_buffer_;
@@ -242,8 +244,6 @@
   bool has_line_terminator_before_next_;
   bool is_pre_parsing_;
 
-  static const int kCharacterLookaheadBufferSize = 1;
-
   // Literal buffer support
   void StartLiteral();
   void AddChar(uc32 ch);