Recognize EMSGSIZE as non-fatal on OS X.

ipc/ipc_channel_posix.cc

Index: ipc/ipc_channel_posix.cc
diff --git a/ipc/ipc_channel_posix.cc b/ipc/ipc_channel_posix.cc
index 0d178d50ddef10c334ba06d3451de638205dcac1..435c572883b7c936c8b3ed41dd7e7106de3340fe 100644
--- a/ipc/ipc_channel_posix.cc
+++ b/ipc/ipc_channel_posix.cc
@@ -241,6 +241,17 @@ bool ClientConnectToFifo(const std::string &pipe_name, int* client_socket) {
   return true;
 }
 
+bool SocketWriteErrorIsRecoverable() {
+#if defined(OS_MACOSX)
+  // On OS X if sendmsg() is trying to send fds between processes and there
+  // isn't enough room in the output buffer to send the fd structure over
+  // atomically then EMSGSIZE is returned.
+  return errno == EAGAIN || errno == EMSGSIZE;
+#else
+  return errno == EAGAIN;
+#endif
+}
+
 }  // namespace
 //------------------------------------------------------------------------------
 
@@ -815,7 +826,7 @@ bool Channel::ChannelImpl::ProcessOutgoingMessages() {
     if (bytes_written > 0)
       msg->file_descriptor_set()->CommitAll();
 
-    if (bytes_written < 0 && errno != EAGAIN) {
+    if (bytes_written < 0 && !SocketWriteErrorIsRecoverable()) {
 #if defined(OS_MACOSX)
       // On OSX writing to a pipe with no listener returns EPERM.
       if (errno == EPERM) {
@@ -830,13 +841,7 @@ bool Channel::ChannelImpl::ProcessOutgoingMessages() {
       PLOG(ERROR) << "pipe error on "
                   << fd_written
                   << " Currently writing message of size:"
-                  << msg->size()
-                  << " msgh.msg_iovlen:"
-                  << msgh.msg_iovlen
-                  << " amt_to_write: "
-                  << amt_to_write
-                  << " num FDs to send:"
-                  << msg->file_descriptor_set()->size();
+                  << msg->size();
       return false;
     }