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

src/runtime.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 2877 matching lines @@
   int unchecked = flag_attr->value();
   RUNTIME_ASSERT((unchecked & ~(READ_ONLY | DONT_ENUM | DONT_DELETE)) == 0);
   RUNTIME_ASSERT(!obj->IsNull());
   LookupResult result;
   obj->LocalLookupRealNamedProperty(name, &result);
 
   PropertyAttributes attr = static_cast<PropertyAttributes>(unchecked);
   // If an existing property is either FIELD, NORMAL or CONSTANT_FUNCTION
   // delete it to avoid running into trouble in DefineAccessor, which
   // handles this incorrectly if the property is readonly (does nothing)
-  if (result.IsValid() &&
+  if (result.IsProperty() &&
       (result.type() == FIELD || result.type() == NORMAL
        || result.type() == CONSTANT_FUNCTION)) {
     obj->DeleteProperty(name, JSObject::NORMAL_DELETION);
   }
   return obj->DefineAccessor(name, flag_setter->value() == 0, fun, attr);
 }
 
 static Object* Runtime_DefineOrRedefineDataProperty(Arguments args) {
   ASSERT(args.length() == 4);
   HandleScope scope;
@@ skipping 5273 matching lines @@
   } else {
     // Handle last resort GC and make sure to allow future allocations
     // to grow the heap without causing GCs (if possible).
     Counters::gc_last_resort_from_js.Increment();
     Heap::CollectAllGarbage(false);
   }
 }
 
 
 } }  // namespace v8::internal