[strong] Refactor ObjectStrength into a replacement for strong boolean args

src/globals.h

Index: src/globals.h
diff --git a/src/globals.h b/src/globals.h
index c73f395cb6808672ffc19863112facb8c32c4752..23a647021d14e4724d881d422f6237c460206630 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -227,11 +227,6 @@ template <typename T, class P = FreeStoreAllocationPolicy> class List;
 // -----------------------------------------------------------------------------
 // Declarations for use in both the preparser and the rest of V8.
 
-enum ObjectStrength {
-  WEAK,
-  FIRM  // strong object
-};
-
 // The Strict Mode (ECMA-262 5th edition, 4.2.2).
 
 enum LanguageMode {
@@ -291,8 +286,27 @@ inline LanguageMode construct_language_mode(bool strict_bit, bool strong_bit) {
 }
 
 
-inline ObjectStrength strength(LanguageMode language_mode) {
-  return is_strong(language_mode) ? FIRM : WEAK;
+enum class Strength : bool {
+  WEAK,
+  FIRM  // strong behaviour
+};
+
+
+inline bool is_strong(Strength strength) { return strength == Strength::FIRM; }
+
+
+inline std::ostream& operator<<(std::ostream& os, const Strength& strength) {
+  return os << (is_strong(strength) ? "firm" : "weak");
+}
+
+
+inline Strength strength(LanguageMode language_mode) {
+  return is_strong(language_mode) ? Strength::FIRM : Strength::WEAK;
+}
+
+
+inline size_t hash_value(Strength strength) {
+  return static_cast<size_t>(strength);
 }