Remove base::subtle::MemoryBarrier

It clashes with MemoryBarrier macro defined in windows.h.

TBR=fdoray@chromium.org
(for updating callers outside of //base)

Bug: 952820
Change-Id: I68c742ed21cea6eb5b10127dea92100fd29d3b3e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1565986
Commit-Queue: Tomasz Moniuszko <tmoniuszko@opera.com>
Reviewed-by: François Doray <fdoray@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#657167}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: bdbaaf4e7e0318fca0cadd1407de810a71309625
diff --git a/src/base/vdso_support.cc b/src/base/vdso_support.cc
index f88aa30..c52fcf9 100644
--- a/src/base/vdso_support.cc
+++ b/src/base/vdso_support.cc
@@ -42,13 +42,10 @@
 #include <fcntl.h>
 #include <stddef.h>   // for ptrdiff_t
 
-#include "base/atomicops.h"  // for MemoryBarrier
 #include "base/logging.h"
 #include "base/dynamic_annotations.h"
 #include "base/basictypes.h"  // for COMPILE_ASSERT
 
-using base::subtle::MemoryBarrier;
-
 #ifndef AT_SYSINFO_EHDR
 #define AT_SYSINFO_EHDR 33
 #endif