Linux: move SyncIPC function from Skia to base.

base/unix_domain_socket_posix.h

 // Copyright (c) 2009 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 BASE_UNIX_DOMAIN_SOCKET_POSIX_H_
 #define BASE_UNIX_DOMAIN_SOCKET_POSIX_H_
 
 #include <sys/types.h>
 #include <vector>
 

[Evan Martin, 2009/06/18 00:36:08]

This file is getting bigger, can you put a description at the top?  ("sync IPCs
for blah blah blah, see this wiki page")

+class Pickle;
+
 namespace base {
 
 // Use sendmsg to write the given msg and include a vector
 // of file descriptors. Returns true iff successful.
 bool SendMsg(int fd, const void* msg, size_t length,
              std::vector<int>& fds);
 // Use recvmsg to read a message and an array of file descriptors. Returns
 // -1 on failure. Note: will read, at most, 16 descriptors.
 ssize_t RecvMsg(int fd, void* msg, size_t length, std::vector<int>* fds);
+// Perform a sendmsg/recvmsg pair by sending the given Pickle as a request
+// along with a file descriptor over which the reply is read.

[Evan Martin, 2009/06/18 00:36:08]

The way this is worded, it sounds like you're sending a file descriptor, which I
don't think you are.

+//   fd: descriptor to send the request on
+//   reply: buffer for the reply
+//   reply_len: size of |reply|
+//   result_fd: (may be NULL) the file descriptor returned in the reply (if any)
+//   request: the bytes to send in the request
+ssize_t SendRecvMsg(int fd, uint8_t* reply, unsigned reply_len, int* result_fd,
+                    const Pickle& request);
 
 }  // namespace base
 
 #endif  // BASE_UNIX_DOMAIN_SOCKET_POSIX_H_