Remove unused sal.h include, pdfium doesn't use _Printf_format_string_.

Remove a bunch of MSVC_ macros that are unused in pdfium at
the moment while here too.

Bug: none
Change-Id: Icef69f71e9cf58ccd44fded507549dccfb44271b
Reviewed-on: https://pdfium-review.googlesource.com/c/50897
Commit-Queue: Nico Weber <thakis@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
diff --git a/third_party/base/compiler_specific.h b/third_party/base/compiler_specific.h
index 59aa479..947cbf3 100644
--- a/third_party/base/compiler_specific.h
+++ b/third_party/base/compiler_specific.h
@@ -7,48 +7,6 @@
 
 #include "build/build_config.h"
 
-#if defined(COMPILER_MSVC)
-
-// For _Printf_format_string_.
-#include <sal.h>
-
-// Macros for suppressing and disabling warnings on MSVC.
-//
-// Warning numbers are enumerated at:
-// http://msdn.microsoft.com/en-us/library/8x5x43k7(VS.80).aspx
-//
-// The warning pragma:
-// http://msdn.microsoft.com/en-us/library/2c8f766e(VS.80).aspx
-//
-// Using __pragma instead of #pragma inside macros:
-// http://msdn.microsoft.com/en-us/library/d9x1s805.aspx
-
-// MSVC_SUPPRESS_WARNING disables warning |n| for the remainder of the line and
-// for the next line of the source file.
-#define MSVC_SUPPRESS_WARNING(n) __pragma(warning(suppress:n))
-
-// MSVC_PUSH_DISABLE_WARNING pushes |n| onto a stack of warnings to be disabled.
-// The warning remains disabled until popped by MSVC_POP_WARNING.
-#define MSVC_PUSH_DISABLE_WARNING(n) __pragma(warning(push)) \
-                                     __pragma(warning(disable:n))
-
-// Pop effects of innermost MSVC_PUSH_* macro.
-#define MSVC_POP_WARNING() __pragma(warning(pop))
-
-#define MSVC_DISABLE_OPTIMIZE() __pragma(optimize("", off))
-#define MSVC_ENABLE_OPTIMIZE() __pragma(optimize("", on))
-
-#else  // Not MSVC
-
-#define _Printf_format_string_
-#define MSVC_SUPPRESS_WARNING(n)
-#define MSVC_PUSH_DISABLE_WARNING(n)
-#define MSVC_POP_WARNING()
-#define MSVC_DISABLE_OPTIMIZE()
-#define MSVC_ENABLE_OPTIMIZE()
-
-#endif  // COMPILER_MSVC
-
 // Annotate a variable indicating it's ok if the variable is not used.
 // (Typically used to silence a compiler warning when the assignment
 // is important for some other reason.)