[wrapper-tracing] Add heap snapshot generator infrastructure

third_party/WebKit/Source/bindings/core/v8/V8PerIsolateData.cpp

 /*
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 388 matching lines @@
 }
 
 void V8PerIsolateData::addActiveScriptWrappable(
     ActiveScriptWrappableBase* wrappable) {
   if (!m_activeScriptWrappables)
     m_activeScriptWrappables = new ActiveScriptWrappableSet();
 
   m_activeScriptWrappables->add(wrappable);
 }
 
+void V8PerIsolateData::TemporaryScriptWrappableVisitorScope::
+    swapWithV8PerIsolateDataVisitor(
+        std::unique_ptr<ScriptWrappableVisitor>& visitor) {
+  ScriptWrappableVisitor* current = currentVisitor(m_isolate);
+  if (current)
+    current->performCleanup();
+
+  V8PerIsolateData::from(m_isolate)->m_scriptWrappableVisitor.swap(visitor);
+  m_isolate->SetEmbedderHeapTracer(visitor.get());
+}
+
 }  // namespace blink