[Interpreter] Ensure we always have an outer register allocation scope.

tools/gyp/v8.gyp

 # Copyright 2012 the V8 project authors. All rights reserved.
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 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
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 #     * Redistributions in binary form must reproduce the above
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@@ skipping 845 matching lines @@
         '../../src/identity-map.cc',
         '../../src/identity-map.h',
         '../../src/interface-descriptors.cc',
         '../../src/interface-descriptors.h',
         '../../src/interpreter/bytecodes.cc',
         '../../src/interpreter/bytecodes.h',
         '../../src/interpreter/bytecode-array-builder.cc',
         '../../src/interpreter/bytecode-array-builder.h',
         '../../src/interpreter/bytecode-array-iterator.cc',
         '../../src/interpreter/bytecode-array-iterator.h',
+        '../../src/interpreter/bytecode-register-allocator.cc',
+        '../../src/interpreter/bytecode-register-allocator.h',
         '../../src/interpreter/bytecode-generator.cc',
         '../../src/interpreter/bytecode-generator.h',
         '../../src/interpreter/bytecode-traits.h',
         '../../src/interpreter/constant-array-builder.cc',
         '../../src/interpreter/constant-array-builder.h',
         '../../src/interpreter/control-flow-builders.cc',
         '../../src/interpreter/control-flow-builders.h',
         '../../src/interpreter/interpreter.cc',
         '../../src/interpreter/interpreter.h',
         '../../src/isolate-inl.h',
@@ skipping 1247 matching lines @@
         }],
         ['want_separate_host_toolset==1', {
           'toolsets': ['host'],
         }, {
           'toolsets': ['target'],
         }],
       ],
     },
   ],
 }