[Object.observe] Lazily allocate callbackInfo structure

test/cctest/test-object-observe.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 411 matching lines @@
   HarmonyIsolate isolate;
   HandleScope scope(isolate.GetIsolate());
   LocalContext context;
   CompileRun(
       "var obj = {};"
       "Object.observe(obj, function(){});"
       "Object.getNotifier(obj);"
       "obj = null;");
   i::Handle<i::JSObject> observation_state =
       i::Isolate::Current()->factory()->observation_state();
-  i::Handle<i::JSWeakMap> observerInfoMap =
+  i::Handle<i::JSWeakMap> callbackInfoMap =
       i::Handle<i::JSWeakMap>::cast(
-          i::GetProperty(observation_state, "observerInfoMap"));
+          i::GetProperty(observation_state, "callbackInfoMap"));
   i::Handle<i::JSWeakMap> objectInfoMap =
       i::Handle<i::JSWeakMap>::cast(
           i::GetProperty(observation_state, "objectInfoMap"));
   i::Handle<i::JSWeakMap> notifierTargetMap =
       i::Handle<i::JSWeakMap>::cast(
           i::GetProperty(observation_state, "notifierTargetMap"));
-  CHECK_EQ(1, NumberOfElements(observerInfoMap));
+  CHECK_EQ(1, NumberOfElements(callbackInfoMap));
   CHECK_EQ(1, NumberOfElements(objectInfoMap));
   CHECK_EQ(1, NumberOfElements(notifierTargetMap));
   HEAP->CollectAllGarbage(i::Heap::kAbortIncrementalMarkingMask);
-  CHECK_EQ(0, NumberOfElements(observerInfoMap));
+  CHECK_EQ(0, NumberOfElements(callbackInfoMap));
   CHECK_EQ(0, NumberOfElements(objectInfoMap));
   CHECK_EQ(0, NumberOfElements(notifierTargetMap));
 }