Library prefix should be an identifier

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 61 matching lines @@
   // Source code line number and column of current token.
   const SourcePosition& CurrentPosition() const {
     return current_token_.position;
   }
 
   static void InitOnce();
 
   // Allocated a private key which is used for name mangling.
   static RawString* AllocatePrivateKey(const Library& library);
 
+  // Return true if str is an identifier.
+  static bool IsIdent(const String& str);
+
  private:
   struct ScanContext {
     ScanContext* next;
     char string_delimiter;
     bool string_is_multiline;
     int  brace_level;
   };
 
   struct KeywordTable {
     Token::Kind kind;
@@ skipping 102 matching lines @@
   const String& private_key_;
 
   SourcePosition c0_pos_;      // Source position of lookahead character c0_.
   KeywordTable keywords_[Token::numKeywords];
 };
 
 
 }  // namespace dart
 
 #endif  // VM_SCANNER_H_