Revert of Temporarily disable double fields unboxing.

src/globals.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_GLOBALS_H_
 #define V8_GLOBALS_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 71 matching lines @@
 #define V8_DEFAULT_STACK_SIZE_KB 864
 #else
 // Slightly less than 1MB, since Windows' default stack size for
 // the main execution thread is 1MB for both 32 and 64-bit.
 #define V8_DEFAULT_STACK_SIZE_KB 984
 #endif
 
 
 // Determine whether double field unboxing feature is enabled.
 #if V8_TARGET_ARCH_64_BIT
-#define V8_DOUBLE_FIELDS_UNBOXING 0
+#define V8_DOUBLE_FIELDS_UNBOXING 1
 #else
 #define V8_DOUBLE_FIELDS_UNBOXING 0
 #endif
 
 
 typedef uint8_t byte;
 typedef byte* Address;
 
 // -----------------------------------------------------------------------------
 // Constants
@@ skipping 734 matching lines @@
 
 inline bool IsSubclassConstructor(FunctionKind kind) {
   DCHECK(IsValidFunctionKind(kind));
   return kind & FunctionKind::kSubclassConstructor;
 }
 } }  // namespace v8::internal
 
 namespace i = v8::internal;
 
 #endif  // V8_GLOBALS_H_