Oilpan: avoid heap allocation in MajorGCWrapperVisitor

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 @@
         v8::UniqueId id(*idPointer);
         if (!m_liveRootGroupIdSet) {
             m_isolate->SetObjectGroupId(liveRoot, id);
             m_liveRootGroupIdSet = true;
             ++m_domObjectsWithPendingActivity;
         }
         return id;
     }
 
     v8::Isolate* m_isolate;
-    WillBePersistentHeapVector<RawPtrWillBeMember<Node>> m_groupsWhichNeedRetainerInfo;
+    Vector<RawPtrWillBeUntracedMember<Node>> m_groupsWhichNeedRetainerInfo;

[haraken, 2015/12/30 16:00:14]

Maybe worth adding a comment to explain why we need to use UntracedMembers.

[sof, 2015/12/30 16:08:01]

added explanatory comment.

     int m_domObjectsWithPendingActivity;
     bool m_liveRootGroupIdSet;
     bool m_constructRetainedObjectInfos;
 };
 
 static unsigned long long usedHeapSize(v8::Isolate* isolate)
 {
     v8::HeapStatistics heapStatistics;
     isolate->GetHeapStatistics(&heapStatistics);
     return heapStatistics.used_heap_size();
@@ skipping 197 matching lines @@
     Visitor* m_visitor;
 };
 
 void V8GCController::traceDOMWrappers(v8::Isolate* isolate, Visitor* visitor)
 {
     DOMWrapperTracer tracer(visitor);
     isolate->VisitHandlesWithClassIds(&tracer);
 }
 
 } // namespace blink