Use an allocation site scratchpad to speed up allocaton site processing during gc.

src/mark-compact.cc

Index: src/mark-compact.cc
diff --git a/src/mark-compact.cc b/src/mark-compact.cc
index c0e1039e3c91018eb1a8cb63d531840d7bd6aad7..1e7809399f6c5a155bad47aafe5394837788663a 100644
--- a/src/mark-compact.cc
+++ b/src/mark-compact.cc
@@ -3361,6 +3361,13 @@ void MarkCompactCollector::EvacuateNewSpaceAndCandidates() {
     EvacuateNewSpace();
   }
 
+  // We have to travers our allocation sites scratchpad which contains raw
+  // pointers before we move objects. During new space evacauation we
+  // gathered pretenuring statistics. The found allocation sites may not be
+  // valid after compacting old space.
+  heap()->ProcessPretenuringFeedback();
+
+
   { GCTracer::Scope gc_scope(tracer_, GCTracer::Scope::MC_EVACUATE_PAGES);
     EvacuatePages();
   }