[wrapper-tracing] Fix V8GCController::getRetainerInfos

third_party/WebKit/Source/bindings/core/v8/V8GCController.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:
  *
  *     * 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
@@ skipping 216 matching lines @@
         !m_firstScriptWrappableTraced) {
       m_firstScriptWrappableTraced = true;
       traceable->traceWrappers(this);
     }
   }
 
  private:
   v8::HeapProfiler::RetainerChildren findV8WrappersDirectlyReachableFrom(
       Node* traceable) {
     CHECK(m_foundV8Wrappers.empty());
-    WTF::AutoReset<bool>(&m_onlyTraceSingleLevel, true);
+    WTF::AutoReset<bool> scope(&m_onlyTraceSingleLevel, true);
     m_firstScriptWrappableTraced = false;
     m_currentParent =
         &v8::Persistent<v8::Value>::Cast(*traceable->rawMainWorldWrapper());
 
     TracePrologue();
     traceable->wrapperTypeInfo()->traceWrappers(this, traceable);
     AdvanceTracing(
         0,
         v8::EmbedderHeapTracer::AdvanceTracingActions(
             v8::EmbedderHeapTracer::ForceCompletionAction::FORCE_COMPLETION));
@@ skipping 18 matching lines @@
 };
 
 // The function |getRetainerInfos| processing all handles on the blink heap,
 // logically grouping together DOM trees (attached and detached) and pending
 // activities, while at the same time finding parent to child relationships
 // for non-Node wrappers. Since we are processing *all* handles there is no
 // way we miss out on a handle. V8 will figure out the liveness information
 // for the provided information itself.
 v8::HeapProfiler::RetainerInfos V8GCController::getRetainerInfos(
     v8::Isolate* isolate) {
-  std::unique_ptr<HeapSnaphotWrapperVisitor> tracer(
-      new HeapSnaphotWrapperVisitor(isolate));
   V8PerIsolateData::TemporaryScriptWrappableVisitorScope scope(
-      isolate, std::move(tracer));
+      isolate, std::unique_ptr<HeapSnaphotWrapperVisitor>(
+                   new HeapSnaphotWrapperVisitor(isolate)));
 
+  HeapSnaphotWrapperVisitor* tracer =
+      reinterpret_cast<HeapSnaphotWrapperVisitor*>(scope.currentVisitor());
   tracer->collectV8Roots();
   tracer->traceV8Roots();
   tracer->tracePendingActivities();
   return v8::HeapProfiler::RetainerInfos{tracer->groups(), tracer->edges()};
 }
 
 class MajorGCWrapperVisitor : public v8::PersistentHandleVisitor {
  public:
   explicit MajorGCWrapperVisitor(v8::Isolate* isolate,
                                  bool constructRetainedObjectInfos)
@@ skipping 389 matching lines @@
   double startTime = WTF::currentTimeMS();
   v8::HandleScope scope(isolate);
   PendingActivityVisitor visitor(isolate, executionContext);
   toIsolate(executionContext)->VisitHandlesWithClassIds(&visitor);
   scanPendingActivityHistogram.count(
       static_cast<int>(WTF::currentTimeMS() - startTime));
   return visitor.pendingActivityFound();
 }
 
 }  // namespace blink