[ic] Make prototypes fast when storing through keyed store ic.

src/ic/ic.cc

Index: src/ic/ic.cc
diff --git a/src/ic/ic.cc b/src/ic/ic.cc
index 02cd939fae2cfecfff04791d7035f9bde949bdea..078e6e4bab01b4c346d9d3cbfd6ad447b216417f 100644
--- a/src/ic/ic.cc
+++ b/src/ic/ic.cc
@@ -2265,6 +2265,10 @@ MaybeHandle<Object> KeyedStoreIC::Store(Handle<Object> object,
     return store_handle;
   }
 
+  if (state() != UNINITIALIZED) {
+    JSObject::MakePrototypesFast(object, kStartAtPrototype, isolate());
+  }
+
   bool use_ic = FLAG_use_ic && !object->IsStringWrapper() &&
                 !object->IsAccessCheckNeeded() && !object->IsJSGlobalProxy();
   if (use_ic && !object->IsSmi()) {