[keys] Postpone shadowed key checking in the KeyAccumulator

src/keys.h

Index: src/keys.h
diff --git a/src/keys.h b/src/keys.h
index ecd3d97c550cf5a8aa80f2aa312c18d1001115ca..045fe97536f1d58caafcb35d6ec89289ea8dce49 100644
--- a/src/keys.h
+++ b/src/keys.h
@@ -83,8 +83,8 @@ class KeyAccumulator final BASE_EMBEDDED {
   }
   // Shadowing keys are used to filter keys. This happens when non-enumerable
   // keys appear again on the prototype chain.
-  void AddShadowKey(Object* key);
-  void AddShadowKey(Handle<Object> key);
+  void AddShadowingKey(Object* key);
+  void AddShadowingKey(Handle<Object> key);
 
  private:
   Maybe<bool> CollectOwnKeys(Handle<JSReceiver> receiver,
@@ -96,6 +96,7 @@ class KeyAccumulator final BASE_EMBEDDED {
   Maybe<bool> AddKeysFromJSProxy(Handle<JSProxy> proxy,
                                  Handle<FixedArray> keys);
   bool IsShadowed(Handle<Object> key);
+  bool HasShadowingKeys();
   Handle<OrderedHashSet> keys() { return Handle<OrderedHashSet>::cast(keys_); }
 
   Isolate* isolate_;
@@ -104,12 +105,15 @@ class KeyAccumulator final BASE_EMBEDDED {
   // result list, a FixedArray containing all collected keys.
   Handle<FixedArray> keys_;
   Handle<JSReceiver> last_non_empty_prototype_;
-  Handle<ObjectHashSet> shadowed_keys_;
+  Handle<ObjectHashSet> shadowing_keys_;
   KeyCollectionMode mode_;
   PropertyFilter filter_;
   bool filter_proxy_keys_ = true;
   bool is_for_in_ = false;
   bool skip_indices_ = false;
+  // For all the keys on the first receiver adding a shadowing key we can skip
+  // the shadow check.
+  bool skip_shadow_check_ = true;
 
   DISALLOW_COPY_AND_ASSIGN(KeyAccumulator);
 };