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

src/property-details.h

 // Copyright 2012 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.
 
 #ifndef V8_PROPERTY_DETAILS_H_
 #define V8_PROPERTY_DETAILS_H_
 
 #include "include/v8.h"
 #include "src/allocation.h"
 #include "src/utils.h"
@@ skipping 230 matching lines @@
 
   Representation representation() const {
     DCHECK(type() != NORMAL);
     return DecodeRepresentation(RepresentationField::decode(value_));
   }
 
   int field_index() const {
     return FieldIndexField::decode(value_);
   }
 
+  inline int field_width_in_words() const;
+
   inline PropertyDetails AsDeleted() const;
 
   static bool IsValidIndex(int index) {
     return DictionaryStorageField::is_valid(index);
   }
 
   bool IsReadOnly() const { return (attributes() & READ_ONLY) != 0; }
   bool IsConfigurable() const { return (attributes() & DONT_DELETE) == 0; }
   bool IsDontEnum() const { return (attributes() & DONT_ENUM) != 0; }
   bool IsDeleted() const { return DeletedField::decode(value_) != 0;}
@@ skipping 34 matching lines @@
   uint32_t value_;
 };
 
 
 std::ostream& operator<<(std::ostream& os,
                          const PropertyAttributes& attributes);
 std::ostream& operator<<(std::ostream& os, const PropertyDetails& details);
 } }  // namespace v8::internal
 
 #endif  // V8_PROPERTY_DETAILS_H_