[builtins] Properly optimize Object.prototype.isPrototypeOf.

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

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_COMPILER_JS_NATIVE_CONTEXT_SPECIALIZATION_H_
 #define V8_COMPILER_JS_NATIVE_CONTEXT_SPECIALIZATION_H_
 
 #include "src/base/flags.h"
 #include "src/compiler/graph-reducer.h"
 #include "src/deoptimize-reason.h"
@@ skipping 127 matching lines @@
   // Adds stability dependencies on all prototypes of every class in
   // {receiver_type} up to (and including) the {holder}.
   void AssumePrototypesStable(MapHandles const& receiver_maps,
                               Handle<JSObject> holder);
 
   // Checks if we can turn the hole into undefined when loading an element
   // from an object with one of the {receiver_maps}; sets up appropriate
   // 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,
                            FeedbackNexus const& nexus,
                            MapHandles* receiver_maps);
 
   // Try to infer maps for the given {receiver} at the current {effect}.
   // If maps are returned then you can be sure that the {receiver} definitely
   // has one of the returned maps at this point in the program (identified
   // by {effect}).
@@ skipping 41 matching lines @@
   DISALLOW_COPY_AND_ASSIGN(JSNativeContextSpecialization);
 };
 
 DEFINE_OPERATORS_FOR_FLAGS(JSNativeContextSpecialization::Flags)
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_JS_NATIVE_CONTEXT_SPECIALIZATION_H_