[builtins] Also migrate String.prototype.toLowerCase/toUpperCase to C++.

src/builtins.cc

 // Copyright 2012 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.
 
 #include "src/builtins.h"
 
 #include "src/api-arguments.h"
 #include "src/api-natives.h"
 #include "src/api.h"
 #include "src/base/once.h"
@@ skipping 4536 matching lines @@
     assembler->Return(assembler->NaNConstant());
     assembler->Bind(&if_positioninbounds);
   }
 
   // Load the character at the {position} from the {receiver}.
   Node* value = assembler->StringCharCodeAt(receiver, position);
   Node* result = assembler->SmiFromWord32(value);
   assembler->Return(result);
 }
 
+// ES6 section 21.1.3.22 String.prototype.toLowerCase ( )
+BUILTIN(StringPrototypeToLowerCase) {
+  HandleScope scope(isolate);
+  TO_THIS_STRING(string, "String.prototype.toLowerCase");
+  ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, string,
+                                     String::ToLowerCase(string));
+  return *string;
+}
+
+// ES6 section 21.1.3.24 String.prototype.toUpperCase ( )
+BUILTIN(StringPrototypeToUpperCase) {
+  HandleScope scope(isolate);
+  TO_THIS_STRING(string, "String.prototype.toUpperCase");
+  ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, string,
+                                     String::ToUpperCase(string));
+  return *string;
+}
+
 // ES6 section 21.1.3.25 String.prototype.trim ()
 BUILTIN(StringPrototypeTrim) {
   HandleScope scope(isolate);
   TO_THIS_STRING(string, "String.prototype.trim");
   return *String::Trim(string, String::kTrim);
 }
 
 // Non-standard WebKit extension
 BUILTIN(StringPrototypeTrimLeft) {
   HandleScope scope(isolate);
@@ skipping 1033 matching lines @@
 BUILTIN_LIST_T(DEFINE_BUILTIN_ACCESSOR_T)
 BUILTIN_LIST_H(DEFINE_BUILTIN_ACCESSOR_H)
 BUILTIN_LIST_DEBUG_A(DEFINE_BUILTIN_ACCESSOR_A)
 #undef DEFINE_BUILTIN_ACCESSOR_C
 #undef DEFINE_BUILTIN_ACCESSOR_A
 #undef DEFINE_BUILTIN_ACCESSOR_T
 #undef DEFINE_BUILTIN_ACCESSOR_H
 
 }  // namespace internal
 }  // namespace v8