GCPrologueCallbackPair 6268 src/heap.cc      GCPrologueCallbackPair pair(callback, gc_type);
GCPrologueCallbackPair 1779 src/heap.h         GCPrologueCallbackPair(GCPrologueCallback callback, GCType gc_type)
GCPrologueCallbackPair 1782 src/heap.h         bool operator==(const GCPrologueCallbackPair& pair) const {
GCPrologueCallbackPair 1788 src/heap.h       List<GCPrologueCallbackPair> gc_prologue_callbacks_;