Remove --experimental-classes flag and related dead code.

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 348 matching lines @@
         '../../src/api.cc',
         '../../src/api.h',
         '../../src/api-natives.cc',
         '../../src/api-natives.h',
         '../../src/arguments.cc',
         '../../src/arguments.h',
         '../../src/assembler.cc',
         '../../src/assembler.h',
         '../../src/assert-scope.h',
         '../../src/assert-scope.cc',
-        '../../src/ast-this-access-visitor.cc',
-        '../../src/ast-this-access-visitor.h',
         '../../src/ast-value-factory.cc',
         '../../src/ast-value-factory.h',
         '../../src/ast-numbering.cc',
         '../../src/ast-numbering.h',
         '../../src/ast.cc',
         '../../src/ast.h',
         '../../src/background-parsing-task.cc',
         '../../src/background-parsing-task.h',
         '../../src/bailout-reason.cc',
         '../../src/bailout-reason.h',
@@ skipping 1432 matching lines @@
         }],
         ['want_separate_host_toolset==1', {
           'toolsets': ['host'],
         }, {
           'toolsets': ['target'],
         }],
       ],
     },
   ],
 }