Migrate some case conversion functions from JS to CPP builtins

src/builtins/builtins-intl.cc

Index: src/builtins/builtins-intl.cc
diff --git a/src/builtins/builtins-intl.cc b/src/builtins/builtins-intl.cc
new file mode 100644
index 0000000000000000000000000000000000000000..96a1e5d8def1212c61d9837f3fb652e8e9641b0e
--- /dev/null
+++ b/src/builtins/builtins-intl.cc
@@ -0,0 +1,32 @@
+// Copyright 2017 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.
+
+#ifdef V8_I18N_SUPPORT
+
+#include "src/builtins/builtins-utils.h"
+#include "src/builtins/builtins.h"
+#include "src/code-stub-assembler.h"

[Jakob Kummerow, 2017/03/18 12:27:32]

This doesn't need the CodeStubAssembler. However, you might want to include
objects-inl.h instead (that's where e.g. String::Flatten lives).

+#include "src/i18n.h"
+
+namespace v8 {
+namespace internal {
+
+BUILTIN(StringPrototypeToLowerCaseI18N) {
+  HandleScope scope(isolate);
+  TO_THIS_STRING(string, "String.prototype.toLowerCase");
+  string = String::Flatten(string);
+  return ConvertCase(string, false, isolate);
+}
+
+BUILTIN(StringPrototypeToUpperCaseI18N) {
+  HandleScope scope(isolate);
+  TO_THIS_STRING(string, "String.prototype.toUpperCase");
+  string = String::Flatten(string);
+  return ConvertCase(string, true, isolate);
+}
+
+}  // namespace internal
+}  // namespace v8
+
+#endif  // V8_I18N_SUPPORT