Compare :lang value case-insensitive in ASCII range

Source/core/css/SelectorChecker.cpp

Index: Source/core/css/SelectorChecker.cpp
diff --git a/Source/core/css/SelectorChecker.cpp b/Source/core/css/SelectorChecker.cpp
index 8c46bd91176849a0eada246d00bb726c8abc55cb..6b882bd448a3b3961b26fdc1b1708b0a48f3352e 100644
--- a/Source/core/css/SelectorChecker.cpp
+++ b/Source/core/css/SelectorChecker.cpp
@@ -964,7 +964,7 @@ bool SelectorChecker::checkPseudoClass(const SelectorCheckingContext& context, u
             else
                 value = element.computeInheritedLanguage();
             const AtomicString& argument = selector.argument();
-            if (value.isEmpty() || !value.startsWith(argument, TextCaseInsensitive))
+            if (value.isEmpty() || !startsWithIgnoringASCIICase(value, argument))
                 break;
             if (value.length() != argument.length() && value[argument.length()] != '-')
                 break;