Allow objects with "" properties to stay fast.

src/runtime.cc

 // Copyright 2012 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 5338 matching lines @@
     name = Handle<String>::cast(converted);
   }
 
   if (name->IsString()) Handle<String>::cast(name)->TryFlatten();
   Handle<Object> result = JSReceiver::DeleteProperty(receiver, name, mode);
   RETURN_IF_EMPTY_HANDLE(isolate, result);
   return *result;
 }
 
 
+RUNTIME_FUNCTION(MaybeObject*, Runtime_SetHiddenProperty) {
+  HandleScope scope(isolate);
+  RUNTIME_ASSERT(args.length() == 3);
+
+  CONVERT_ARG_HANDLE_CHECKED(JSObject, object, 0);
+  CONVERT_ARG_HANDLE_CHECKED(String, key, 1);
+  CONVERT_ARG_HANDLE_CHECKED(Object, value, 2);
+  return *JSObject::SetHiddenProperty(object, key, value);
+}
+
+
 RUNTIME_FUNCTION(MaybeObject*, Runtime_SetProperty) {
   HandleScope scope(isolate);
   RUNTIME_ASSERT(args.length() == 4 || args.length() == 5);
 
   CONVERT_ARG_HANDLE_CHECKED(Object, object, 0);
   CONVERT_ARG_HANDLE_CHECKED(Object, key, 1);
   CONVERT_ARG_HANDLE_CHECKED(Object, value, 2);
   CONVERT_SMI_ARG_CHECKED(unchecked_attributes, 3);
   RUNTIME_ASSERT(
       (unchecked_attributes & ~(READ_ONLY | DONT_ENUM | DONT_DELETE)) == 0);
@@ skipping 9596 matching lines @@
     // Handle last resort GC and make sure to allow future allocations
     // to grow the heap without causing GCs (if possible).
     isolate->counters()->gc_last_resort_from_js()->Increment();
     isolate->heap()->CollectAllGarbage(Heap::kNoGCFlags,
                                        "Runtime::PerformGC");
   }
 }
 
 
 } }  // namespace v8::internal