[turbofan] Properly handle dictionary maps in the prototype chain.

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"
 
@@ skipping 62 matching lines @@
                               LanguageMode language_mode);
   Reduction ReduceNamedAccess(Node* node, Node* value,
                               MapHandleList const& receiver_maps,
                               Handle<Name> name, AccessMode access_mode,
                               LanguageMode language_mode,
                               Node* index = nullptr);
 
   Reduction ReduceSoftDeoptimize(Node* node);
 
   // Adds stability dependencies on all prototypes of every class in
-  // {receiver_type} up to (and including) the {holder}.
-  void AssumePrototypesStable(Type* receiver_type,
-                              Handle<Context> native_context,
-                              Handle<JSObject> holder);
+  // {receiver_type} up to (and including) the {holder} if the maps
+  // are stable, otherwise falls back to inserting runtime map checks
+  // on the prototypes.
+  Node* CheckPrototypeMaps(Type* receiver_type, Handle<Context> native_context,
+                           Handle<JSObject> holder, Node* effect,
+                           Node* control);
 
   // Extract receiver maps from {nexus} and filter based on {receiver} if
   // possible.
   bool ExtractReceiverMaps(Node* receiver, Node* effect,
                            FeedbackNexus const& nexus,
                            MapHandleList* receiver_maps);
 
   // Try to infer a map for the given {receiver} at the current {effect}.
   // If a map is returned then you can be sure that the {receiver} definitely
   // has the returned map at this point in the program (identified by {effect}).
@@ skipping 28 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_