Reland "In-object double fields unboxing (for 64-bit only)."

BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # TODO(jochen): These will need to be user-settable to support standalone V8
 # builds.
 v8_compress_startup_data = "off"
 v8_deprecation_warnings = false
 v8_enable_disassembler = false
 v8_enable_gdbjit = false
@@ skipping 764 matching lines @@
     "src/interface-descriptors.h",
     "src/interpreter-irregexp.cc",
     "src/interpreter-irregexp.h",
     "src/isolate.cc",
     "src/isolate.h",
     "src/json-parser.h",
     "src/json-stringifier.h",
     "src/jsregexp-inl.h",
     "src/jsregexp.cc",
     "src/jsregexp.h",
+    "src/layout-descriptor-inl.h",
+    "src/layout-descriptor.cc",
+    "src/layout-descriptor.h",
     "src/list-inl.h",
     "src/list.h",
     "src/lithium-allocator-inl.h",
     "src/lithium-allocator.cc",
     "src/lithium-allocator.h",
     "src/lithium-codegen.cc",
     "src/lithium-codegen.h",
     "src/lithium.cc",
     "src/lithium.h",
     "src/liveedit.cc",
@@ skipping 659 matching lines @@
     deps = [
       ":v8_base",
       ":v8_nosnapshot",
     ]
   }
 
   direct_dependent_configs = [ ":external_config" ]
 }
 
 }