Revert of Remove IPC::BrokerableAttachment.

ipc/ipc_channel_nacl.h

Index: ipc/ipc_channel_nacl.h
diff --git a/ipc/ipc_channel_nacl.h b/ipc/ipc_channel_nacl.h
index 45d64cea559c873ca86eae1de848d22c24a8e687..52ff321b08816e982ab7424eb6a6a81d00c7c481 100644
--- a/ipc/ipc_channel_nacl.h
+++ b/ipc/ipc_channel_nacl.h
@@ -62,7 +62,7 @@
                      int buffer_len,
                      int* bytes_read) override;
   bool ShouldDispatchInputMessage(Message* msg) override;
-  bool GetAttachments(Message* msg) override;
+  bool GetNonBrokeredAttachments(Message* msg) override;
   bool DidEmptyInputBuffers() override;
   void HandleInternalMessage(const Message& msg) override;
 
@@ -102,8 +102,11 @@
   //                 2 above in NaCl eventually.
   // When ReadData is called, it pulls the bytes out of this queue in order.
   std::deque<linked_ptr<std::vector<char> > > read_queue_;
-  // Queue of file descriptor attachments extracted from imc_recvmsg messages.
-  std::vector<scoped_refptr<MessageAttachment>> input_attachments_;
+  // Queue of file descriptors extracted from imc_recvmsg messages.
+  // NOTE: The implementation assumes underlying storage here is contiguous, so
+  // don't change to something like std::deque<> without changing the
+  // implementation!
+  std::vector<int> input_fds_;
 
   // This queue is used when a message is sent prior to Connect having been
   // called. Normally after we're connected, the queue is empty.