[wrapper-tracing] Add heap snapshot generator infrastructure

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

Index: third_party/WebKit/Source/bindings/core/v8/V8PerIsolateData.cpp
diff --git a/third_party/WebKit/Source/bindings/core/v8/V8PerIsolateData.cpp b/third_party/WebKit/Source/bindings/core/v8/V8PerIsolateData.cpp
index 36bdec1839d60e3e065a7e0f18e12c74babca12a..cb16358744644028c53a5bb817c9aa02f77c92a0 100644
--- a/third_party/WebKit/Source/bindings/core/v8/V8PerIsolateData.cpp
+++ b/third_party/WebKit/Source/bindings/core/v8/V8PerIsolateData.cpp
@@ -406,4 +406,15 @@ void V8PerIsolateData::addActiveScriptWrappable(
   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