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

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 123d1c229c719b14b1a1b6601ee3e6af8398e474..60ac93428dab054da703ec4287e991c49b8837a5 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -1510,6 +1510,7 @@ class Smi: public Object {
   void SmiPrint(std::ostream& os) const;  // NOLINT
   DECLARE_VERIFIER(Smi)
 
+  V8_EXPORT_PRIVATE static Smi* const kZero;
   static const int kMinValue =
       (static_cast<unsigned int>(-1)) << (kSmiValueSize - 1);
   static const int kMaxValue = -(kMinValue + 1);
@@ -2872,7 +2873,7 @@ class WeakFixedArray : public FixedArray {
   inline int Length() const;
 
   inline bool IsEmptySlot(int index) const;
-  static Object* Empty() { return Smi::FromInt(0); }
+  static Object* Empty() { return Smi::kZero; }
 
   class Iterator {
    public:
@@ -11216,7 +11217,7 @@ class DebugInfo: public Struct {
   // Get the number of break points for this function.
   int GetBreakPointCount();
 
-  static Smi* uninitialized() { return Smi::FromInt(0); }
+  static Smi* uninitialized() { return Smi::kZero; }
 
   inline bool HasDebugBytecodeArray();
   inline bool HasDebugCode();