Revert of Add debug checks to catch PropertyCell::cast failures.

src/lookup.cc

Index: src/lookup.cc
diff --git a/src/lookup.cc b/src/lookup.cc
index 2b69aa67959f957a0fc283a6b4d30892257ec081..e5eecce234116e1098c8bd23e5c2fdc6fc1bb9d0 100644
--- a/src/lookup.cc
+++ b/src/lookup.cc
@@ -256,7 +256,6 @@
   if (holder_map_->is_dictionary_map()) {
     result = holder->property_dictionary()->ValueAt(number_);
     if (holder_map_->IsGlobalObjectMap()) {
-      DCHECK(result->IsPropertyCell());
       result = PropertyCell::cast(result)->value();
     }
   } else if (property_details_.type() == v8::internal::DATA) {
@@ -311,7 +310,6 @@
   Handle<JSObject> holder = GetHolder<JSObject>();
   Handle<GlobalObject> global = Handle<GlobalObject>::cast(holder);
   Object* value = global->property_dictionary()->ValueAt(dictionary_entry());
-  DCHECK(value->IsPropertyCell());
   return Handle<PropertyCell>(PropertyCell::cast(value));
 }