[turbofan] Non-dictionary prototype maps are always stable.

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/compiler/simplified-operator.h"
@@ skipping 54 matching lines @@
                                  PropertyAccessMode access_mode,
                                  PropertyAccessInfo* access_info);
   bool ComputePropertyAccessInfos(MapHandleList const& maps, Handle<Name> name,
                                   PropertyAccessMode access_mode,
                                   ZoneVector<PropertyAccessInfo>* access_infos);
 
   struct ScriptContextTableLookupResult;
   bool LookupInScriptContextTable(Handle<Name> name,
                                   ScriptContextTableLookupResult* result);
 
+  // Adds stability dependencies on all prototypes of every class in
+  // {receiver_type} up to (and including) the {holder}.
+  void AssumePrototypesStable(Type* receiver_type, Handle<JSObject> holder);
+
   Graph* graph() const;
   JSGraph* jsgraph() const { return jsgraph_; }
   Isolate* isolate() const;
   Factory* factory() const;
   CommonOperatorBuilder* common() const;
   JSOperatorBuilder* javascript() const;
   SimplifiedOperatorBuilder* simplified() const;
   MachineOperatorBuilder* machine() const;
   Flags flags() const { return flags_; }
   Handle<GlobalObject> global_object() const { return global_object_; }
   CompilationDependencies* dependencies() const { return dependencies_; }
   Zone* zone() const { return zone_; }
 
   JSGraph* const jsgraph_;
   Flags const flags_;
   Handle<GlobalObject> global_object_;
   CompilationDependencies* const dependencies_;
   Zone* const zone_;
 
   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_