Add STLSetDifference to stl_util.h, because std::set_difference is extremely

base/base.gyp

 # 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.
 
 {
   'variables': {
     'chromium_code': 1,
   },
   'includes': [
     '../build/win_precompile.gypi',
@@ skipping 492 matching lines @@
         'process_util_unittest.cc',
         'process_util_unittest_ios.cc',
         'process_util_unittest_mac.h',
         'process_util_unittest_mac.mm',
         'profiler/tracked_time_unittest.cc',
         'rand_util_unittest.cc',
         'scoped_native_library_unittest.cc',
         'scoped_observer.h',
         'sha1_unittest.cc',
         'shared_memory_unittest.cc',
+        'stl_util_unittest.cc',
         'string16_unittest.cc',
         'string_number_conversions_unittest.cc',
         'string_piece_unittest.cc',
         'string_split_unittest.cc',
         'string_tokenizer_unittest.cc',
         'string_util_unittest.cc',
         'stringize_macros_unittest.cc',
         'stringprintf_unittest.cc',
         'synchronization/cancellation_flag_unittest.cc',
         'synchronization/condition_variable_unittest.cc',
@@ skipping 581 matching lines @@
             'base_unittests.isolate',
           ],
           'sources': [
             'base_unittests.isolate',
           ],
         },
       ],
     }],
   ],
 }