Convert String array index/length hash to BitField

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index 277d320588d04ccbdb92a715e6bdc147333beb85..a7b880e4ea8c539d6c70c80fab25f013fa29ce61 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -9668,7 +9668,7 @@ bool String::SlowAsArrayIndex(uint32_t* index) {
     uint32_t field = hash_field();
     if ((field & kIsNotArrayIndexMask) != 0) return false;
     // Isolate the array index form the full hash field.
-    *index = (kArrayIndexHashMask & field) >> kHashShift;
+    *index = ArrayIndexValueBits::decode(field);
     return true;
   } else {
     return ComputeArrayIndex(index);
@@ -9726,8 +9726,8 @@ uint32_t StringHasher::MakeArrayIndexHash(uint32_t value, int length) {
   ASSERT(TenToThe(String::kMaxCachedArrayIndexLength) <
          (1 << String::kArrayIndexValueBits));
 
-  value <<= String::kHashShift;
-  value |= length << String::kArrayIndexHashLengthShift;
+  value <<= String::ArrayIndexValueBits::kShift;
+  value |= length << String::ArrayIndexLengthBits::kShift;
 
   ASSERT((value & String::kIsNotArrayIndexMask) == 0);
   ASSERT((length > String::kMaxCachedArrayIndexLength) ||