Remove the LookupResult IsValid method because it is confusing....

src/x64/stub-cache-x64.cc

 // Copyright 2010 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 381 matching lines @@
   ASSERT(!holder->GetNamedInterceptor()->getter()->IsUndefined());
 
   // Check that the receiver isn't a smi.
   __ JumpIfSmi(receiver, miss);
 
   // Check that the maps haven't changed.
   Register reg =
       stub_compiler->CheckPrototypes(object, receiver, holder,
                                      scratch1, scratch2, name, miss);
 
-  if (lookup->IsValid() && lookup->IsCacheable()) {
+  if (lookup->IsProperty() && lookup->IsCacheable()) {
     compiler->CompileCacheable(masm,
                                stub_compiler,
                                receiver,
                                reg,
                                scratch1,
                                scratch2,
                                holder,
                                lookup,
                                name,
                                miss);
@@ skipping 1440 matching lines @@
   __ Jump(generic_construct_stub, RelocInfo::CODE_TARGET);
 
   // Return the generated code.
   return GetCode();
 }
 
 
 #undef __
 
 } }  // namespace v8::internal