Deleted OS_WIN and all Windows specific files from base.

base/atomicops.h

Index: base/atomicops.h
diff --git a/base/atomicops.h b/base/atomicops.h
index 6a5371c75c295e87d33e21fc16ddc89d4937e4d5..d69b5315ff36267102b93d65e877c8b78a7eefc7 100644
--- a/base/atomicops.h
+++ b/base/atomicops.h
@@ -39,15 +39,6 @@
 #include "base/base_export.h"
 #include "build/build_config.h"
 
-#if defined(OS_WIN) && defined(ARCH_CPU_64_BITS)
-// windows.h #defines this (only on x64). This causes problems because the
-// public API also uses MemoryBarrier at the public name for this fence. So, on
-// X64, undef it, and call its documented
-// (http://msdn.microsoft.com/en-us/library/windows/desktop/ms684208.aspx)
-// implementation directly.
-#undef MemoryBarrier
-#endif
-
 namespace base {
 namespace subtle {
 
@@ -183,9 +174,6 @@ BASE_EXPORT extern struct AtomicOps_x86CPUFeatureStruct
 #else  // Otherwise use a platform specific implementation.
 #  if defined(THREAD_SANITIZER)
 #    error "Thread sanitizer must use the portable atomic operations"
-#  elif (defined(OS_WIN) && defined(COMPILER_MSVC) && \
-         defined(ARCH_CPU_X86_FAMILY))
-#    include "base/atomicops_internals_x86_msvc.h"
 #  elif defined(OS_MACOSX)
 #    include "base/atomicops_internals_mac.h"
 #  elif defined(OS_NACL)