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

test/unittests/unittests.gyp

 # Copyright 2014 the V8 project 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': {
     'v8_code': 1,
   },
   'includes': ['../../build/toolchain.gypi', '../../build/features.gypi'],
   'targets': [
@@ skipping 79 matching lines @@
         'compiler/simplified-operator-unittest.cc',
         'compiler/state-values-utils-unittest.cc',
         'compiler/tail-call-optimization-unittest.cc',
         'compiler/typer-unittest.cc',
         'compiler/value-numbering-reducer-unittest.cc',
         'compiler/zone-pool-unittest.cc',
         'counters-unittest.cc',
         'interpreter/bytecodes-unittest.cc',
         'interpreter/bytecode-array-builder-unittest.cc',
         'interpreter/bytecode-array-iterator-unittest.cc',
+        'interpreter/bytecode-register-allocator-unittest.cc',
         'interpreter/constant-array-builder-unittest.cc',
         'libplatform/default-platform-unittest.cc',
         'libplatform/task-queue-unittest.cc',
         'libplatform/worker-thread-unittest.cc',
         'heap/bitmap-unittest.cc',
         'heap/gc-idle-time-handler-unittest.cc',
         'heap/memory-reducer-unittest.cc',
         'heap/heap-unittest.cc',
         'heap/scavenge-job-unittest.cc',
         'locked-queue-unittest.cc',
@@ skipping 80 matching lines @@
             '../../build/isolate.gypi',
           ],
           'sources': [
             'unittests.isolate',
           ],
         },
       ],
     }],
   ],
 }