Introduce a PrototypeIterator template and use it all over the place

src/objects.h

 // Copyright 2012 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_OBJECTS_H_
 #define V8_OBJECTS_H_
 
 #include "src/allocation.h"
 #include "src/assert-scope.h"
 #include "src/builtins.h"
@@ skipping 1487 matching lines @@
       Isolate* isolate,
       Handle<Object> object,
       uint32_t index);
 
   MUST_USE_RESULT static MaybeHandle<Object> GetElementWithReceiver(
       Isolate* isolate,
       Handle<Object> object,
       Handle<Object> receiver,
       uint32_t index);
 
-  // Return the object's prototype (might be Heap::null_value()).
+  // Return the object's prototype (might be Heap::null_value()). Please use a
+  // PrototypeIterator instead.
+  //
+  // TODO(jochen): Make these private.
   Object* GetPrototype(Isolate* isolate);
   static Handle<Object> GetPrototype(Isolate* isolate, Handle<Object> object);
 
   // Returns the permanent hash code associated with this object. May return
   // undefined if not yet created.
   Object* GetHash();
 
   // Returns the permanent hash code associated with this object depending on
   // the actual object type. May create and store a hash code if needed and none
   // exists.
@@ skipping 442 matching lines @@
       Handle<JSReceiver> object,
       Handle<Name> name);
 
   static inline PropertyAttributes GetElementAttribute(
       Handle<JSReceiver> object,
       uint32_t index);
   static inline PropertyAttributes GetOwnElementAttribute(
       Handle<JSReceiver> object,
       uint32_t index);
 
-  // Return the object's prototype (might be Heap::null_value()).
+  // Return the object's prototype (might be Heap::null_value()). Use a
+  // PrototypeIterator instead.
+  //
+  // TODO(jochen): Make this method private.
   inline Object* GetPrototype();
 
   // Return the constructor function (may be Heap::null_value()).
   inline Object* GetConstructor();
 
   // Retrieves a permanent object identity hash code. The undefined value might
   // be returned in case no hash was created yet.
   inline Object* GetIdentityHash();
 
   // Retrieves a permanent object identity hash code. May create and store a
@@ skipping 9162 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_