[builtins] Properly optimize Object.prototype.isPrototypeOf.

src/compiler/js-native-context-specialization.h

Index: src/compiler/js-native-context-specialization.h
diff --git a/src/compiler/js-native-context-specialization.h b/src/compiler/js-native-context-specialization.h
index da92ae79f0a4b0853bd0556c85405e977a0fda13..5819bce7f4ec8d67cfe11aac07a372e9c6df2a9a 100644
--- a/src/compiler/js-native-context-specialization.h
+++ b/src/compiler/js-native-context-specialization.h
@@ -145,17 +145,6 @@ class JSNativeContextSpecialization final : public AdvancedReducer {
   // code dependencies and might use the array protector cell.
   bool CanTreatHoleAsUndefined(MapHandles const& receiver_maps);
 
-  // Checks if we know at compile time that the {receiver} either definitely
-  // has the {prototype} in it's prototype chain, or the {receiver} definitely
-  // doesn't have the {prototype} in it's prototype chain.
-  enum InferHasInPrototypeChainResult {
-    kIsInPrototypeChain,
-    kIsNotInPrototypeChain,
-    kMayBeInPrototypeChain
-  };
-  InferHasInPrototypeChainResult InferHasInPrototypeChain(
-      Node* receiver, Node* effect, Handle<JSReceiver> prototype);
-
   // Extract receiver maps from {nexus} and filter based on {receiver} if
   // possible.
   bool ExtractReceiverMaps(Node* receiver, Node* effect,