Check ASCIIness of lhs, not this.

src/objects.cc

 // Copyright 2006-2009 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 4720 matching lines @@
 
   if (StringShape(lhs).IsSequentialAscii() &&
       StringShape(rhs).IsSequentialAscii()) {
     const char* str1 = SeqAsciiString::cast(lhs)->GetChars();
     const char* str2 = SeqAsciiString::cast(rhs)->GetChars();
     return CompareRawStringContents(Vector<const char>(str1, len),
                                     Vector<const char>(str2, len));
   }
 
   if (lhs->IsFlat()) {
-    if (IsAsciiRepresentation()) {
+    if (lhs->IsAsciiRepresentation()) {
       Vector<const char> vec1 = lhs->ToAsciiVector();
       if (rhs->IsFlat()) {
         if (rhs->IsAsciiRepresentation()) {
           Vector<const char> vec2 = rhs->ToAsciiVector();
           return CompareRawStringContents(vec1, vec2);
         } else {
           VectorIterator<char> buf1(vec1);
           VectorIterator<uc16> ib(rhs->ToUC16Vector());
           return CompareStringContents(&buf1, &ib);
         }
@@ skipping 4059 matching lines @@
   if (break_point_objects()->IsUndefined()) return 0;
   // Single beak point.
   if (!break_point_objects()->IsFixedArray()) return 1;
   // Multiple break points.
   return FixedArray::cast(break_point_objects())->length();
 }
 #endif
 
 
 } }  // namespace v8::internal