Add Smi::Zero and replace all Smi::FromInt(0) calls

src/builtins/builtins-conversion.cc

 // Copyright 2016 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/builtins/builtins.h"
 #include "src/builtins/builtins-utils.h"
 #include "src/code-factory.h"
 
 namespace v8 {
 namespace internal {
@@ skipping 372 matching lines @@
       assembler->Goto(&loop);
     }
 
     assembler->Bind(&return_len);
     assembler->Return(var_len.value());
 
     assembler->Bind(&return_two53minus1);
     assembler->Return(assembler->NumberConstant(kMaxSafeInteger));
 
     assembler->Bind(&return_zero);
-    assembler->Return(assembler->SmiConstant(Smi::FromInt(0)));
+    assembler->Return(assembler->SmiConstant(Smi::kZero));
   }
 }
 
 void Builtins::Generate_ToInteger(CodeStubAssembler* assembler) {
   typedef TypeConversionDescriptor Descriptor;
 
   compiler::Node* input = assembler->Parameter(Descriptor::kArgument);
   compiler::Node* context = assembler->Parameter(Descriptor::kContext);
 
   assembler->Return(assembler->ToInteger(context, input));
@@ skipping 73 matching lines @@
   typedef TypeofDescriptor Descriptor;
 
   Node* object = assembler->Parameter(Descriptor::kObject);
   Node* context = assembler->Parameter(Descriptor::kContext);
 
   assembler->Return(assembler->Typeof(object, context));
 }
 
 }  // namespace internal
 }  // namespace v8