Stop disabling compiler warning 4481, v8 edition.

build/standalone.gypi

 # 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 827 matching lines @@
 
           # TODO(jochen): These warnings are level 4. They will be slowly
           # removed as code is fixed.
           4100, # Unreferenced formal parameter
           4121, # Alignment of a member was sensitive to packing
           4244, # Conversion from 'type1' to 'type2', possible loss of data
           4302, # Truncation from 'type 1' to 'type 2'
           4309, # Truncation of constant value
           4311, # Pointer truncation from 'type' to 'type'
           4312, # Conversion from 'type1' to 'type2' of greater size
-          4481, # Nonstandard extension used: override specifier 'keyword'
           4505, # Unreferenced local function has been removed
           4510, # Default constructor could not be generated
           4512, # Assignment operator could not be generated
           4610, # Object can never be instantiated
           4800, # Forcing value to bool.
           4838, # Narrowing conversion. Doesn't seem to be very useful.
           4995, # 'X': name was marked as #pragma deprecated
           4996, # 'X': was declared deprecated (for GetVersionEx).
 
           # These are variable shadowing warnings that are new in VS2015. We
@@ skipping 503 matching lines @@
               '-fsanitize=cfi-vcall',
               '-fsanitize=cfi-derived-cast',
               '-fsanitize=cfi-unrelated-cast',
             ],
           }],
         ],
       },
     }],
   ],
 }