Migrate some case conversion functions from JS to CPP builtins

src/builtins/builtins.h

Index: src/builtins/builtins.h
diff --git a/src/builtins/builtins.h b/src/builtins/builtins.h
index 2137129d759a0d302e2ab73ac57f9ea357238505..d7378da91d8b15d698448daa581e50d29daefb7c 100644
--- a/src/builtins/builtins.h
+++ b/src/builtins/builtins.h
@@ -51,7 +51,7 @@ class Isolate;
 // DBG: Builtin in platform-dependent assembly, used by the debugger.
 //      Args: name
 
-#define BUILTIN_LIST(CPP, API, TFJ, TFS, ASM, ASH, DBG)                        \
+#define BUILTIN_LIST_BASE(CPP, API, TFJ, TFS, ASM, ASH, DBG)                   \
   ASM(Abort)                                                                   \
   /* Code aging */                                                             \
   CODE_AGE_LIST_WITH_ARG(DECLARE_CODE_AGE_BUILTIN, ASM)                        \
@@ -791,13 +791,10 @@ class Isolate;
   CPP(StringPrototypeStartsWith)                                               \
   /* ES6 section 21.1.3.25 String.prototype.toString () */                     \
   TFJ(StringPrototypeToString, 0)                                              \
-  /* ES #sec-string.prototype.tolocalelowercase */                             \
+  /* (obsolete) Unibrow string functions */                                    \
   CPP(StringPrototypeToLocaleLowerCase)                                        \
-  /* ES #sec-string.prototype.tolocaleuppercase */                             \
   CPP(StringPrototypeToLocaleUpperCase)                                        \
-  /* ES #sec-string.prototype.tolowercase */                                   \
   CPP(StringPrototypeToLowerCase)                                              \
-  /* ES #sec-string.prototype.touppercase */                                   \
   CPP(StringPrototypeToUpperCase)                                              \
   CPP(StringPrototypeTrim)                                                     \
   CPP(StringPrototypeTrimLeft)                                                 \
@@ -876,6 +873,24 @@ class Isolate;
   /* proposal-async-iteration/#sec-async-iterator-value-unwrap-functions */    \
   TFJ(AsyncIteratorValueUnwrap, 1)
 
+#ifdef V8_I18N_SUPPORT
+#define BUILTIN_LIST(CPP, API, TFJ, TFS, ASM, ASH, DBG)          \
+  BUILTIN_LIST_BASE(CPP, API, TFJ, TFS, ASM, ASH, DBG)           \
+                                                                 \
+  /* TODO(jwolfe): implement the *Locale* variants like below */ \
+  /* ES #sec-string.prototype.tolocalelowercase */               \
+  /* CPP(StringPrototypeToLocaleLowerCaseI18N) */                \
+  /* ES #sec-string.prototype.tolocaleuppercase */               \
+  /* CPP(StringPrototypeToLocaleUpperCaseI18N) */                \
+  /* ES #sec-string.prototype.tolowercase */                     \
+  CPP(StringPrototypeToLowerCaseI18N)                            \
+  /* ES #sec-string.prototype.touppercase */                     \
+  CPP(StringPrototypeToUpperCaseI18N)
+#else
+#define BUILTIN_LIST(CPP, API, TFJ, TFS, ASM, ASH, DBG) \
+  BUILTIN_LIST_BASE(CPP, API, TFJ, TFS, ASM, ASH, DBG)
+#endif  // V8_I18N_SUPPORT
+
 #define BUILTIN_PROMISE_REJECTION_PREDICTION_LIST(V) \
   V(AsyncFromSyncIteratorPrototypeNext)              \
   V(AsyncFromSyncIteratorPrototypeReturn)            \