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diff --git a/gn/base/compiler_specific.h b/gn/base/compiler_specific.h
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+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_COMPILER_SPECIFIC_H_
+#define BASE_COMPILER_SPECIFIC_H_
+
+#include "util/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))
+
+// MSVC_PUSH_WARNING_LEVEL pushes |n| as the global warning level.  The level
+// remains in effect until popped by MSVC_POP_WARNING().  Use 0 to disable all
+// warnings.
+#define MSVC_PUSH_WARNING_LEVEL(n) __pragma(warning(push, 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_PUSH_WARNING_LEVEL(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.)
+// Use like:
+//   int x = ...;
+//   ALLOW_UNUSED_LOCAL(x);
+#define ALLOW_UNUSED_LOCAL(x) (void)x
+
+// Annotate a typedef or function indicating it's ok if it's not used.
+// Use like:
+//   typedef Foo Bar ALLOW_UNUSED_TYPE;
+#if defined(COMPILER_GCC) || defined(__clang__)
+#define ALLOW_UNUSED_TYPE __attribute__((unused))
+#else
+#define ALLOW_UNUSED_TYPE
+#endif
+
+// Annotate a function indicating it should not be inlined.
+// Use like:
+//   NOINLINE void DoStuff() { ... }
+#if defined(COMPILER_GCC)
+#define NOINLINE __attribute__((noinline))
+#elif defined(COMPILER_MSVC)
+#define NOINLINE __declspec(noinline)
+#else
+#define NOINLINE
+#endif
+
+#if COMPILER_GCC && defined(NDEBUG)
+#define ALWAYS_INLINE inline __attribute__((__always_inline__))
+#elif COMPILER_MSVC && defined(NDEBUG)
+#define ALWAYS_INLINE __forceinline
+#else
+#define ALWAYS_INLINE inline
+#endif
+
+// Specify memory alignment for structs, classes, etc.
+// Use like:
+//   class ALIGNAS(16) MyClass { ... }
+//   ALIGNAS(16) int array[4];
+//
+// In most places you can use the C++11 keyword "alignas", which is preferred.
+//
+// But compilers have trouble mixing __attribute__((...)) syntax with
+// alignas(...) syntax.
+//
+// Doesn't work in clang or gcc:
+//   struct alignas(16) __attribute__((packed)) S { char c; };
+// Works in clang but not gcc:
+//   struct __attribute__((packed)) alignas(16) S2 { char c; };
+// Works in clang and gcc:
+//   struct alignas(16) S3 { char c; } __attribute__((packed));
+//
+// There are also some attributes that must be specified *before* a class
+// definition: visibility (used for exporting functions/classes) is one of
+// these attributes. This means that it is not possible to use alignas() with a
+// class that is marked as exported.
+#if defined(COMPILER_MSVC)
+#define ALIGNAS(byte_alignment) __declspec(align(byte_alignment))
+#elif defined(COMPILER_GCC)
+#define ALIGNAS(byte_alignment) __attribute__((aligned(byte_alignment)))
+#endif
+
+// Annotate a function indicating the caller must examine the return value.
+// Use like:
+//   int foo() WARN_UNUSED_RESULT;
+// To explicitly ignore a result, see |ignore_result()| in base/macros.h.
+#undef WARN_UNUSED_RESULT
+#if defined(COMPILER_GCC) || defined(__clang__)
+#define WARN_UNUSED_RESULT __attribute__((warn_unused_result))
+#else
+#define WARN_UNUSED_RESULT
+#endif
+
+// Tell the compiler a function is using a printf-style format string.
+// |format_param| is the one-based index of the format string parameter;
+// |dots_param| is the one-based index of the "..." parameter.
+// For v*printf functions (which take a va_list), pass 0 for dots_param.
+// (This is undocumented but matches what the system C headers do.)
+#if defined(COMPILER_GCC) || defined(__clang__)
+#define PRINTF_FORMAT(format_param, dots_param) \
+  __attribute__((format(printf, format_param, dots_param)))
+#else
+#define PRINTF_FORMAT(format_param, dots_param)
+#endif
+
+// WPRINTF_FORMAT is the same, but for wide format strings.
+// This doesn't appear to yet be implemented in any compiler.
+// See http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38308 .
+#define WPRINTF_FORMAT(format_param, dots_param)
+// If available, it would look like:
+//   __attribute__((format(wprintf, format_param, dots_param)))
+
+// Sanitizers annotations.
+#if defined(__has_attribute)
+#if __has_attribute(no_sanitize)
+#define NO_SANITIZE(what) __attribute__((no_sanitize(what)))
+#endif
+#endif
+#if !defined(NO_SANITIZE)
+#define NO_SANITIZE(what)
+#endif
+
+// MemorySanitizer annotations.
+#if defined(MEMORY_SANITIZER) && !defined(OS_NACL)
+#include <sanitizer/msan_interface.h>
+
+// Mark a memory region fully initialized.
+// Use this to annotate code that deliberately reads uninitialized data, for
+// example a GC scavenging root set pointers from the stack.
+#define MSAN_UNPOISON(p, size) __msan_unpoison(p, size)
+
+// Check a memory region for initializedness, as if it was being used here.
+// If any bits are uninitialized, crash with an MSan report.
+// Use this to sanitize data which MSan won't be able to track, e.g. before
+// passing data to another process via shared memory.
+#define MSAN_CHECK_MEM_IS_INITIALIZED(p, size) \
+  __msan_check_mem_is_initialized(p, size)
+#else  // MEMORY_SANITIZER
+#define MSAN_UNPOISON(p, size)
+#define MSAN_CHECK_MEM_IS_INITIALIZED(p, size)
+#endif  // MEMORY_SANITIZER
+
+// DISABLE_CFI_PERF -- Disable Control Flow Integrity for perf reasons.
+#if !defined(DISABLE_CFI_PERF)
+#if defined(__clang__) && defined(OFFICIAL_BUILD)
+#define DISABLE_CFI_PERF __attribute__((no_sanitize("cfi")))
+#else
+#define DISABLE_CFI_PERF
+#endif
+#endif
+
+// Macro useful for writing cross-platform function pointers.
+#if !defined(CDECL)
+#if defined(OS_WIN)
+#define CDECL __cdecl
+#else  // defined(OS_WIN)
+#define CDECL
+#endif  // defined(OS_WIN)
+#endif  // !defined(CDECL)
+
+// Macro for hinting that an expression is likely to be false.
+#if !defined(UNLIKELY)
+#if defined(COMPILER_GCC) || defined(__clang__)
+#define UNLIKELY(x) __builtin_expect(!!(x), 0)
+#else
+#define UNLIKELY(x) (x)
+#endif  // defined(COMPILER_GCC)
+#endif  // !defined(UNLIKELY)
+
+#if !defined(LIKELY)
+#if defined(COMPILER_GCC) || defined(__clang__)
+#define LIKELY(x) __builtin_expect(!!(x), 1)
+#else
+#define LIKELY(x) (x)
+#endif  // defined(COMPILER_GCC)
+#endif  // !defined(LIKELY)
+
+// Compiler feature-detection.
+// clang.llvm.org/docs/LanguageExtensions.html#has-feature-and-has-extension
+#if defined(__has_feature)
+#define HAS_FEATURE(FEATURE) __has_feature(FEATURE)
+#else
+#define HAS_FEATURE(FEATURE) 0
+#endif
+
+// Macro for telling -Wimplicit-fallthrough that a fallthrough is intentional.
+#if defined(__clang__)
+#define FALLTHROUGH [[clang::fallthrough]]
+#else
+#define FALLTHROUGH
+#endif
+
+#endif  // BASE_COMPILER_SPECIFIC_H_