Keep prototype maps in dictionary mode until ICs see them

src/ic/ic.cc

Index: src/ic/ic.cc
diff --git a/src/ic/ic.cc b/src/ic/ic.cc
index 066b3b45aab85507c35c8b0e7f5b952cd5dd9e5d..bafaffff7eaf5cf7392eb5cf3b19d93e46f8d592 100644
--- a/src/ic/ic.cc
+++ b/src/ic/ic.cc
@@ -227,7 +227,6 @@ bool IC::AddressIsOptimizedCode() const {
   return host->kind() == Code::OPTIMIZED_FUNCTION;
 }
 
-
 static void LookupForRead(LookupIterator* it) {
   for (; it->IsFound(); it->Next()) {
     switch (it->state()) {
@@ -641,6 +640,9 @@ MaybeHandle<Object> LoadIC::Load(Handle<Object> object, Handle<Name> name) {
     }
   }
 
+  if (state() != UNINITIALIZED) {
+    JSObject::MakePrototypesFast(object, kStartAtReceiver, isolate());
+  }
   // Named lookup in the object.
   LookupIterator it(object, name);
   LookupForRead(&it);
@@ -1530,6 +1532,9 @@ MaybeHandle<Object> StoreIC::Store(Handle<Object> object, Handle<Name> name,
     return TypeError(MessageTemplate::kNonObjectPropertyStore, object, name);
   }
 
+  if (state() != UNINITIALIZED) {
+    JSObject::MakePrototypesFast(object, kStartAtPrototype, isolate());
+  }
   LookupIterator it(object, name);
   if (FLAG_use_ic) UpdateCaches(&it, value, store_mode);