[stubs] Port KeyedStoreIC_Megamorphic stub to Turbofan

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index 4c72b3e932aaeb55a94041b51762e209c2a3eb61..ef0b883e8fbbcba1fb87abd6a34df4077e89fa4a 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -15915,6 +15915,14 @@ bool AllocationSite::DigestTransitionFeedback(Handle<AllocationSite> site,
   return result;
 }
 
+AllocationSiteMode AllocationSite::GetMode(ElementsKind from, ElementsKind to) {
+  if (IsFastSmiElementsKind(from) &&
+      IsMoreGeneralElementsKindTransition(from, to)) {
+    return TRACK_ALLOCATION_SITE;
+  }
+
+  return DONT_TRACK_ALLOCATION_SITE;
+}
 
 const char* AllocationSite::PretenureDecisionName(PretenureDecision decision) {
   switch (decision) {