[destructuring] Refactor duplicate parameter name detection.

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 598 matching lines @@
         '../../src/double.h',
         '../../src/dtoa.cc',
         '../../src/dtoa.h',
         '../../src/effects.h',
         '../../src/elements-kind.cc',
         '../../src/elements-kind.h',
         '../../src/elements.cc',
         '../../src/elements.h',
         '../../src/execution.cc',
         '../../src/execution.h',
+        '../../src/expression-classifier.h',
         '../../src/extensions/externalize-string-extension.cc',
         '../../src/extensions/externalize-string-extension.h',
         '../../src/extensions/free-buffer-extension.cc',
         '../../src/extensions/free-buffer-extension.h',
         '../../src/extensions/gc-extension.cc',
         '../../src/extensions/gc-extension.h',
         '../../src/extensions/statistics-extension.cc',
         '../../src/extensions/statistics-extension.h',
         '../../src/extensions/trigger-failure-extension.cc',
         '../../src/extensions/trigger-failure-extension.h',
@@ skipping 1257 matching lines @@
         }],
         ['want_separate_host_toolset==1', {
           'toolsets': ['host'],
         }, {
           'toolsets': ['target'],
         }],
       ],
     },
   ],
 }