Move Smi::kZero definition to the header

src/objects.cc

 // Copyright 2015 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.
 
 #include "src/objects.h"
 
 #include <cmath>
 #include <iomanip>
 #include <memory>
 #include <sstream>
@@ skipping 2185 matching lines @@
   if (v.value->IsSmi()) {
     Smi::cast(v.value)->SmiPrint(os);
   } else {
     // TODO(svenpanne) Const-correct HeapObjectShortPrint!
     HeapObject* obj = const_cast<HeapObject*>(HeapObject::cast(v.value));
     obj->HeapObjectShortPrint(os);
   }
   return os;
 }
 
-// Declaration of the static Smi::kZero constant.
-Smi* const Smi::kZero(nullptr);
-
 void Smi::SmiPrint(std::ostream& os) const {  // NOLINT
   os << value();
 }
 
 
 // Should a word be prefixed by 'a' or 'an' in order to read naturally in
 // English?  Returns false for non-ASCII or words that don't start with
 // a capital letter.  The a/an rule follows pronunciation in English.
 // We don't use the BBC's overcorrect "an historic occasion" though if
 // you speak a dialect you may well say "an 'istoric occasion".
@@ skipping 18216 matching lines @@
       // depend on this.
       return DICTIONARY_ELEMENTS;
     }
     DCHECK_LE(kind, LAST_ELEMENTS_KIND);
     return kind;
   }
 }
 
 }  // namespace internal
 }  // namespace v8