Add safe numerics classes, imported from Chromium

tools/gyp/v8.gyp

 # Copyright 2012 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 #       copyright notice, this list of conditions and the following
 #       disclaimer in the documentation and/or other materials provided
@@ skipping 1064 matching lines @@
         '../../src/base/atomicops_internals_mips_gcc.h',
         '../../src/base/atomicops_internals_tsan.h',
         '../../src/base/atomicops_internals_x86_gcc.cc',
         '../../src/base/atomicops_internals_x86_gcc.h',
         '../../src/base/atomicops_internals_x86_msvc.h',
         '../../src/base/build_config.h',
         '../../src/base/lazy-instance.h',
         '../../src/base/macros.h',
         '../../src/base/once.cc',
         '../../src/base/once.h',
+        '../../src/base/safe_conversions.h',
+        '../../src/base/safe_conversions_impl.h',
+        '../../src/base/safe_math.h',
+        '../../src/base/safe_math_impl.h',
         '../../src/base/win32-headers.h',
       ],
       'conditions': [
         ['want_separate_host_toolset==1', {
           'toolsets': ['host', 'target'],
         }, {
           'toolsets': ['target'],
         }],
         ['component=="shared_library"', {
           'defines': [
@@ skipping 147 matching lines @@
         }],
         ['v8_compress_startup_data=="bz2"', {
           'libraries': [
             '-lbz2',
           ]
         }],
       ],
     },
   ],
 }