[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 f01c10044e9815d02c861075058e399b5a4356a7..cde58c9d58ab78855bfce07b39a47041c27acd63 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -233,11 +233,6 @@ 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 {
@@ -297,8 +292,32 @@ inline LanguageMode construct_language_mode(bool strict_bit, bool strong_bit) {
 }
 
 
-inline ObjectStrength strength(LanguageMode language_mode) {
-  return is_strong(language_mode) ? FIRM : WEAK;
+// Strong mode behaviour must sometimes be signalled by a two valued enum where
+// caching is involved, to prevent sloppy and strict mode from being incorrectly
+// differentiated.
+enum class Strength : bool {
+  WEAK,   // sloppy, strict behaviour
+  STRONG  // strong behaviour
+};
+
+
+inline bool is_strong(Strength strength) {
+  return strength == Strength::STRONG;
+}
+
+
+inline std::ostream& operator<<(std::ostream& os, const Strength& strength) {
+  return os << (is_strong(strength) ? "strong" : "weak");
+}
+
+
+inline Strength strength(LanguageMode language_mode) {
+  return is_strong(language_mode) ? Strength::STRONG : Strength::WEAK;
+}
+
+
+inline size_t hash_value(Strength strength) {
+  return static_cast<size_t>(strength);
 }