Stop disabling compiler warning 4481, PDFium edition.

build/standalone.gypi

 # Copyright 2014 PDFium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # Definitions to be used when building stand-alone PDFium binaries.
 
 {
   'variables': {
     'component%': 'static_library',
     'clang%': 0,
@@ skipping 243 matching lines @@
       # to use setjmp/longjmp for e.g. JPEG decode error handling, which
       # means we have to turn off this warning (and be careful about how
       # object destruction happens in such cases).
       4611,
 
       # TODO(thestig): 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
-      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
       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
       # should work through these at some point -- they may be removed from
@@ skipping 165 matching lines @@
       ],
     }],  # OS=="linux" or OS=="mac"
     ["use_goma==1", {
       'make_global_settings': [
         ['CC_wrapper', '<(gomadir)/gomacc'],
         ['CXX_wrapper', '<(gomadir)/gomacc'],
       ],
     }],  # use_goma==1
   ],
 }