[serializer] allocate global proxy with the expected size.

test/cctest/test-serialize.cc

 // Copyright 2007-2010 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 2366 matching lines @@
     {
       // Add additional context. This context implicitly *does* serialize
       // the global proxy, and upon deserialization one has to be created
       // in the bootstrapper from the global object template.
       // Side effects from extensions are persisted.
       v8::HandleScope handle_scope(isolate);
       v8::Local<v8::ObjectTemplate> global_template =
           v8::ObjectTemplate::New(isolate);
       v8::Local<v8::FunctionTemplate> callback =
           v8::FunctionTemplate::New(isolate, SerializedCallback);
+      global_template->SetInternalFieldCount(3);
       global_template->Set(v8_str("f"), callback);
       global_template->SetHandler(v8::NamedPropertyHandlerConfiguration(
           NamedPropertyGetterForSerialization));
       global_template->SetAccessor(v8_str("y"), AccessorForSerialization);
       v8::Local<v8::Context> context =
           v8::Context::New(isolate, &extensions, global_template);
       v8::Context::Scope context_scope(context);
       ExpectInt32("f()", 42);
       ExpectInt32("g()", 12);
       ExpectInt32("h()", 13);
@@ skipping 51 matching lines @@
           ExpectInt32("f()", 42);
           ExpectInt32("g()", 12);
           ExpectInt32("h()", 13);
           ExpectInt32("i()", 24);
           ExpectInt32("j()", 25);
           ExpectInt32("o.p", 8);
           ExpectInt32("x", 2016);
         }
 
         v8::Local<v8::Object> global = context->Global();
+        CHECK_EQ(3, global->InternalFieldCount());
         context->DetachGlobal();
 
         // New context, but reuse global proxy.
         v8::ExtensionConfiguration* no_extensions = nullptr;
         v8::Local<v8::Context> context2 =
             v8::Context::FromSnapshot(isolate, 0, no_extensions, global)
                 .ToLocalChecked();
         {
           v8::Context::Scope context_scope(context2);
           ExpectInt32("f()", 42);
@@ skipping 12 matching lines @@
   }
   delete[] blob.data;
 }
 
 TEST(SerializationMemoryStats) {
   FLAG_profile_deserialization = true;
   FLAG_always_opt = false;
   v8::StartupData blob = v8::V8::CreateSnapshotDataBlob();
   delete[] blob.data;
 }