Revert 63600 - Thread IO safety: annotate file_util, and block IO thread from...

base/shared_memory_posix.cc

Index: base/shared_memory_posix.cc
===================================================================
--- base/shared_memory_posix.cc	(revision 63629)
+++ base/shared_memory_posix.cc	(working copy)
@@ -14,7 +14,6 @@
 #include "base/logging.h"
 #include "base/platform_thread.h"
 #include "base/safe_strerror_posix.h"
-#include "base/thread_restrictions.h"
 #include "base/utf_string_conversions.h"
 
 namespace base {
@@ -147,11 +146,6 @@
                                 int posix_flags, uint32 size) {
   DCHECK(mapped_file_ == -1);
 
-  // This function theoretically can block on the disk, but realistically
-  // the temporary files we create will just go into the buffer cache
-  // and be deleted before they ever make it out to disk.
-  base::ThreadRestrictions::ScopedAllowIO allow_io;
-
   file_util::ScopedFILE file_closer;
   FILE *fp;