Do not compare case-insensitive for 16bit pseudo identifier

Source/core/css/parser/CSSSelectorParser.cpp

 // Copyright 2014 The Chromium 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 "config.h"
 #include "core/css/parser/CSSSelectorParser.h"
 
 #include "core/css/CSSSelectorList.h"
 #include "core/css/StyleSheetContents.h"
 #include "core/frame/UseCounter.h"
@@ skipping 260 matching lines @@
         range.consume();
         colons++;
     }
 
     const CSSParserToken& token = range.peek();
     if (token.type() != IdentToken && token.type() != FunctionToken)
         return nullptr;
 
     OwnPtr<CSSParserSelector> selector = CSSParserSelector::create();
     selector->setMatch(colons == 1 ? CSSSelector::PseudoClass : CSSSelector::PseudoElement);
-    selector->setValue(AtomicString(String(token.value()).lower()));
+    String value = token.value();
+    selector->setValue(AtomicString(value.is8Bit() ? value.lower() : value));
 
     if (token.type() == IdentToken) {
         range.consume();
         if (selector->pseudoType() == CSSSelector::PseudoUnknown)
             return nullptr;
         return selector.release();
     }
 
     CSSParserTokenRange block = range.consumeBlock();
     block.consumeWhitespace();
@@ skipping 385 matching lines @@
                 context.useCounter()->count(feature);
             if (current->relation() == CSSSelector::ShadowDeep)
                 context.useCounter()->count(UseCounter::CSSDeepCombinator);
             if (current->selectorList())
                 recordSelectorStats(context, *current->selectorList());
         }
     }
 }
 
 } // namespace blink