Use ICU case conversion/transliterator for case conversion behind a flag

src/js/icu-case-mapping.js

+// Copyright 2016 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+(function(global, utils) {
+"use strict";
+
+%CheckIsBootstrapping();
+
+var GlobalString = global.String;
+var OverrideFunction = utils.OverrideFunction;
+var MakeTypeError;
+var LocaleConvertCase = utils.ImportNow("LocaleConvertCase");

[Dan Ehrenberg, 2016/05/04 00:13:08]

Rather than using ImportNow (generally dispreferred), since LocaleConvertCase is
called from a function declaration, you can import it using utils.Import.

[jungshik at Google, 2016/05/04 19:02:58]

Done.

+
+utils.Import(function(from) {
+  MakeTypeError = from.MakeTypeError;
+});
+
+OverrideFunction(GlobalString.prototype, 'toLowerCase', function() {

[jungshik at Google, 2016/05/04 19:02:58]

offline, you're worried about actually defining functions in this file instead
of just installing them. 

Would this be better, then?

OverrideFunction(GlobalString.prototype, 'toLowerCase', toLowerCaseICU);

where |toLowerCaseICU| is defined in i18n.js.

I found an example in harmony-regexp-exec.js exactly doing that. I'll make a
change. 

[Dan Ehrenberg, 2016/05/04 19:06:37]

That's what I was suggesting, though if you found that performance is already
good in this configuration, then that might not be necessary. Note that in this
case, you'll need to use ImportNow. Eventually, the flag will be switched to be
flipped on all the time and this file will be merged into i18n.js, so this is
just about performance during the transition.

+    if (!IS_UNDEFINED(new.target)) {
+      throw MakeTypeError(kOrdinaryFunctionCalledAsConstructor);
+    }
+    CHECK_OBJECT_COERCIBLE(this, "String.prototype.toLowerCase");
+    var s = TO_STRING(this);
+    return %StringToLowerCaseI18N(s);
+  }
+);
+
+OverrideFunction(GlobalString.prototype, 'toUpperCase', function() {
+    if (!IS_UNDEFINED(new.target)) {
+      throw MakeTypeError(kOrdinaryFunctionCalledAsConstructor);
+    }
+    CHECK_OBJECT_COERCIBLE(this, "String.prototype.toLowerCase");
+    var s = TO_STRING(this);
+    return %StringToUpperCaseI18N(s);
+  }
+);
+
+OverrideFunction(GlobalString.prototype, 'toLocaleLowerCase', function() {
+    if (!IS_UNDEFINED(new.target)) {
+      throw MakeTypeError(kOrdinaryFunctionCalledAsConstructor);
+    }
+    CHECK_OBJECT_COERCIBLE(this, "String.prototype.toLocaleLowerCase");
+    return LocaleConvertCase(TO_STRING(this), arguments[0], false);
+  }
+);
+
+OverrideFunction(GlobalString.prototype, 'toLocaleUpperCase', function() {
+    if (!IS_UNDEFINED(new.target)) {
+      throw MakeTypeError(kOrdinaryFunctionCalledAsConstructor);
+    }
+    CHECK_OBJECT_COERCIBLE(this, "String.prototype.toLocaleUpperCase");
+    return LocaleConvertCase(TO_STRING(this), arguments[0], true);
+  }
+);
+
+})