Eagerly follow transitions to existing maps while json parsing.

src/objects.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 2797 matching lines @@
       return Handle<Object>();
     }
     trap = Handle<Object>(derived);
   }
 
   bool threw;
   return Execution::Call(trap, handler, argc, argv, &threw);
 }
 
 
+void JSObject::AddFastPropertyUsingMap(Handle<JSObject> object,
+                                       Handle<Map> map) {
+  CALL_HEAP_FUNCTION_VOID(
+      object->GetIsolate(),
+      object->AddFastPropertyUsingMap(*map));
+}
+
+
 MaybeObject* JSObject::SetPropertyForResult(LookupResult* result,
                                             String* name_raw,
                                             Object* value_raw,
                                             PropertyAttributes attributes,
                                             StrictModeFlag strict_mode,
                                             StoreFromKeyed store_mode) {
   Heap* heap = GetHeap();
   // Make sure that the top context does not change when doing callbacks or
   // interceptor calls.
   AssertNoContextChange ncc;
@@ skipping 10701 matching lines @@
   set_year(Smi::FromInt(year), SKIP_WRITE_BARRIER);
   set_month(Smi::FromInt(month), SKIP_WRITE_BARRIER);
   set_day(Smi::FromInt(day), SKIP_WRITE_BARRIER);
   set_weekday(Smi::FromInt(weekday), SKIP_WRITE_BARRIER);
   set_hour(Smi::FromInt(hour), SKIP_WRITE_BARRIER);
   set_min(Smi::FromInt(min), SKIP_WRITE_BARRIER);
   set_sec(Smi::FromInt(sec), SKIP_WRITE_BARRIER);
 }
 
 } }  // namespace v8::internal