ipc: Make a new class PlaceholderBrokerableAttachment.

ipc/ipc_message_attachment_set.h

 // Copyright (c) 2011 The Chromium 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 IPC_IPC_MESSAGE_ATTACHMENT_SET_H_
 #define IPC_IPC_MESSAGE_ATTACHMENT_SET_H_
 
 #include <vector>
 
 #include "base/basictypes.h"
@@ skipping 42 matching lines @@
   //   returns: an attachment, or nullptr on error
   scoped_refptr<MessageAttachment> GetAttachmentAt(unsigned index);
 
   // This must be called after transmitting the descriptors returned by
   // PeekDescriptors. It marks all the descriptors as consumed and closes those
   // which are auto-close.
   void CommitAll();
 
   // Returns a vector of all brokerable attachments.
   std::vector<const BrokerableAttachment*> PeekBrokerableAttachments() const;
-  std::vector<scoped_refptr<BrokerableAttachment>>
-  GetBrokerableAttachmentsForUpdating();
+
+  // Replaces a placeholder brokerable attachment with |attachment|, matching
+  // them by their id.
+  void ReplacePlaceholderWithAttachment(
+      const scoped_refptr<BrokerableAttachment>& attachment);
 
 #if defined(OS_POSIX)
   // This is the maximum number of descriptors per message. We need to know this
   // because the control message kernel interface has to be given a buffer which
   // is large enough to store all the descriptor numbers. Otherwise the kernel
   // tells us that it truncated the control data and the extra descriptors are
   // lost.
   //
   // In debugging mode, it's a fatal error to try and add more than this number
   // of descriptors to a MessageAttachmentSet.
@@ skipping 41 matching lines @@
   // all the descriptors have been read (with GetNthDescriptor). Secondly, we
   // can check that they are read in order.
   mutable unsigned consumed_descriptor_highwater_;
 
   DISALLOW_COPY_AND_ASSIGN(MessageAttachmentSet);
 };
 
 }  // namespace IPC
 
 #endif  // IPC_IPC_MESSAGE_ATTACHMENT_SET_H_