[proxies] Implement [[Set]].

src/lookup.h

Index: src/lookup.h
diff --git a/src/lookup.h b/src/lookup.h
index 8486beceb3989c4d987c3ff0ca62a045fd468e8a..7d689560b8f7efa5d106d1018fd42c26faa3e9cb 100644
--- a/src/lookup.h
+++ b/src/lookup.h
@@ -206,6 +206,10 @@ class LookupIterator final BASE_EMBEDDED {
 
   bool HolderIsReceiverOrHiddenPrototype() const;
 
+  bool check_prototype_chain() const {
+    return (configuration_ & kPrototypeChain) != 0;
+  }
+
   /* ACCESS_CHECK */
   bool HasAccess() const;
 
@@ -283,9 +287,6 @@ class LookupIterator final BASE_EMBEDDED {
   bool check_interceptor() const {
     return (configuration_ & kInterceptor) != 0;
   }
-  bool check_prototype_chain() const {
-    return (configuration_ & kPrototypeChain) != 0;
-  }
   int descriptor_number() const {
     DCHECK(has_property_);
     DCHECK(!holder_map_->is_dictionary_map());