Deleted OS_WIN and all Windows specific files from base.

base/numerics/safe_numerics_unittest.cc

Index: base/numerics/safe_numerics_unittest.cc
diff --git a/base/numerics/safe_numerics_unittest.cc b/base/numerics/safe_numerics_unittest.cc
index 6f9a966c0156431e654e71d483d81083fe555690..224c8f4ab289daa6bbcc6ed12229dfc627c73b30 100644
--- a/base/numerics/safe_numerics_unittest.cc
+++ b/base/numerics/safe_numerics_unittest.cc
@@ -29,13 +29,6 @@ using base::internal::RANGE_OVERFLOW;
 using base::internal::RANGE_UNDERFLOW;
 using base::enable_if;
 
-// These tests deliberately cause arithmetic overflows. If the compiler is
-// aggressive enough, it can const fold these overflows. Disable warnings about
-// overflows for const expressions.
-#if defined(OS_WIN)
-#pragma warning(disable:4756)
-#endif
-
 // Helper macros to wrap displaying the conversion types and line numbers.
 #define TEST_EXPECTED_VALIDITY(expected, actual)                           \
   EXPECT_EQ(expected, CheckedNumeric<Dst>(actual).validity())              \