Update V8 to r6768 as required by WebKit r78450

Change-Id: Ib8868ff7147a76547a8d1d85f257ebe8546a3d3f
diff --git a/src/preparser.h b/src/preparser.h
index 66fad3b..b7fa6c7 100644
--- a/src/preparser.h
+++ b/src/preparser.h
@@ -243,6 +243,8 @@
     return scanner_->Next();
   }
 
+  bool peek_any_identifier();
+
   void Consume(i::Token::Value token) { Next(); }
 
   void Expect(i::Token::Value token, bool* ok) {