Update from https://crrev.com/308331

base/port.h

 // Copyright (c) 2006-2008 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_PORT_H_
 #define BASE_PORT_H_
 
 #include <stdarg.h>
 #include "build/build_config.h"
 
 // DEPRECATED: Use ...LL and ...ULL suffixes.
 // TODO(viettrungluu): Delete these. These are only here until |GG_(U)INT64_C|
 // are deleted (some other header files (re)define |GG_(U)INT64_C|, so our
 // definitions of them must exactly match theirs).
 #ifdef COMPILER_MSVC
 #define GG_LONGLONG(x) x##I64
 #define GG_ULONGLONG(x) x##UI64
 #else
 #define GG_LONGLONG(x) x##LL
 #define GG_ULONGLONG(x) x##ULL
 #endif
 
 // DEPRECATED: In Chromium, we force-define __STDC_CONSTANT_MACROS, so you can
 // just use the regular (U)INTn_C macros from <stdint.h>.
 // TODO(viettrungluu): Remove the remaining GG_(U)INTn_C macros.
 #define GG_INT64_C(x)   GG_LONGLONG(x)
 #define GG_UINT64_C(x)  GG_ULONGLONG(x)
 
-// It's possible for functions that use a va_list, such as StringPrintf, to
-// invalidate the data in it upon use.  The fix is to make a copy of the
-// structure before using it and use that copy instead.  va_copy is provided
-// for this purpose.  MSVC does not provide va_copy, so define an
-// implementation here.  It is not guaranteed that assignment is a copy, so the
-// StringUtil.VariableArgsFunc unit test tests this capability.
-#if defined(COMPILER_GCC)
-#define GG_VA_COPY(a, b) (va_copy(a, b))
-#elif defined(COMPILER_MSVC)
-#define GG_VA_COPY(a, b) (a = b)
-#endif
-
 // Define an OS-neutral wrapper for shared library entry points
 #if defined(OS_WIN)
 #define API_CALL __stdcall
 #else
 #define API_CALL
 #endif
 
 #endif  // BASE_PORT_H_