[turbofan] Make Factory::NewNumber() always return the minus_zero_value.

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 49 matching lines @@
         'compiler/node-matchers-unittest.cc',
         'compiler/node-test-utils.cc',
         'compiler/node-test-utils.h',
         'compiler/opcodes-unittest.cc',
         'compiler/register-allocator-unittest.cc',
         'compiler/select-lowering-unittest.cc',
         'compiler/simplified-operator-reducer-unittest.cc',
         'compiler/simplified-operator-unittest.cc',
         'compiler/value-numbering-reducer-unittest.cc',
         'compiler/zone-pool-unittest.cc',
+        'factory-unittest.cc',
         'libplatform/default-platform-unittest.cc',
         'libplatform/task-queue-unittest.cc',
         'libplatform/worker-thread-unittest.cc',
         'heap/gc-idle-time-handler-unittest.cc',
         'run-all-unittests.cc',
         'test-utils.h',
         'test-utils.cc',
       ],
       'conditions': [
         ['v8_target_arch=="arm"', {
@@ skipping 52 matching lines @@
           'direct_dependent_settings': {
             'cflags!': [
               '-pedantic',
             ],
           },
         }],
       ],
     },
   ],
 }