[Interpreter] Add a simple dead-code elimination bytecode optimizer.

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.
 
 # Please keep this file in sync with BUILD.gn.
 
 {
   'variables': {
     'v8_code': 1,
   },
@@ skipping 82 matching lines @@
         '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-array-writer-unittest.cc',
+        'interpreter/bytecode-dead-code-optimizer-unittest.cc',
         'interpreter/bytecode-peephole-optimizer-unittest.cc',
         'interpreter/bytecode-pipeline-unittest.cc',
         'interpreter/bytecode-register-allocator-unittest.cc',
         'interpreter/bytecode-register-optimizer-unittest.cc',
         'interpreter/constant-array-builder-unittest.cc',
         'interpreter/interpreter-assembler-unittest.cc',
         'interpreter/interpreter-assembler-unittest.h',
         'interpreter/source-position-table-unittest.cc',
         'libplatform/default-platform-unittest.cc',
         'libplatform/task-queue-unittest.cc',
@@ skipping 109 matching lines @@
             '../../gypfiles/isolate.gypi',
           ],
           'sources': [
             'unittests.isolate',
           ],
         },
       ],
     }],
   ],
 }