ipc: Create an unforgeable mechanism to get the process id of the sender.

ipc/ipc_channel_nacl.h

 // Copyright (c) 2012 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_CHANNEL_NACL_H_
 #define IPC_IPC_CHANNEL_NACL_H_
 
 #include <deque>
 #include <string>
 
@@ skipping 51 matching lines @@
   void CallOnChannelConnected();
 
   // ChannelReader implementation.
   ReadState ReadData(char* buffer,
                      int buffer_len,
                      int* bytes_read) override;
   bool ShouldDispatchInputMessage(Message* msg) override;
   bool GetNonBrokeredAttachments(Message* msg) override;
   bool DidEmptyInputBuffers() override;
   void HandleInternalMessage(const Message& msg) override;
+  base::ProcessId GetSenderPID() override;
 
   Mode mode_;
   bool waiting_connect_;
 
   // The pipe used for communication.
   int pipe_;
 
   // The "name" of our pipe.  On Windows this is the global identifier for
   // the pipe.  On POSIX it's used as a key in a local map of file descriptors.
   // For NaCl, we don't actually support looking up file descriptors by name,
@@ skipping 38 matching lines @@
 
   // |broker_| must outlive this instance.
   AttachmentBroker* broker_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(ChannelNacl);
 };
 
 }  // namespace IPC
 
 #endif  // IPC_IPC_CHANNEL_NACL_H_