Move Posix file utils to the base namespace.

base/sync_socket_posix.cc

Index: base/sync_socket_posix.cc
diff --git a/base/sync_socket_posix.cc b/base/sync_socket_posix.cc
index ba843608319a002aa622afea362e54edb24a6e5b..5bb893aae87319a80aeeabb83ba0aea23edca349 100644
--- a/base/sync_socket_posix.cc
+++ b/base/sync_socket_posix.cc
@@ -113,7 +113,7 @@ size_t SyncSocket::Receive(void* buffer, size_t length) {
   DCHECK_LE(length, kMaxMessageLength);
   DCHECK_NE(handle_, kInvalidHandle);
   char* charbuffer = static_cast<char*>(buffer);
-  if (file_util::ReadFromFD(handle_, charbuffer, length))
+  if (ReadFromFD(handle_, charbuffer, length))
     return length;
   return 0;
 }