POSIX: Add code for shuffling file descriptors.

base/process_util.h

Index: base/process_util.h
diff --git a/base/process_util.h b/base/process_util.h
index a692870c7e5c5540c8f1d0b9fdec81ff40bb8c2b..d20a0f9abc1c029d3ab12d13645ced7af56ec934 100644
--- a/base/process_util.h
+++ b/base/process_util.h
@@ -44,6 +44,8 @@ struct IoCounters {
   unsigned long long WriteTransferCount;
   unsigned long long OtherTransferCount;
 };
+
+#include "base/file_descriptor_shuffle.h"
 #endif
 
 #if defined(OS_MACOSX)
@@ -82,7 +84,14 @@ ProcessId GetProcId(ProcessHandle process);
 #if defined(OS_POSIX)
 // Sets all file descriptors to close on exec except for stdin, stdout
 // and stderr.
+// TODO(agl): remove this function
+// WARNING: do not use. It's inherently race-prone in the face of
+// multi-threading.
 void SetAllFDsToCloseOnExec();
+// Close all file descriptors, expect those which are a destination in the
+// given multimap. Only call this function in a child process where you know
+// that there aren't any other threads.
+void CloseSuperfluousFds(const base::InjectiveMultimap& saved_map);
 #endif
 
 #if defined(OS_WIN)