Make SpaceSplitString::set() faster

Source/core/dom/SpaceSplitString.cpp

 /*
  * Copyright (C) 2007 David Smith (catfish.man@gmail.com)
  * Copyright (C) 2007, 2008, 2011, 2012 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 140 matching lines @@
     return map;
 }
 
 void SpaceSplitString::set(const AtomicString& inputString, CaseFolding caseFolding)
 {
     if (inputString.isNull()) {
         clear();
         return;
     }
 
-    String string(inputString.string());
-    if (caseFolding == ShouldFoldCase && hasNonASCIIOrUpper(string))
+    if (caseFolding == ShouldFoldCase && hasNonASCIIOrUpper(inputString.string())) {
+        String string(inputString.string());
         string = string.foldCase();
-
-    m_data = Data::create(AtomicString(string));
+        m_data = Data::create(AtomicString(string));
+    } else {
+        m_data = Data::create(inputString);
+    }
 }
 
 SpaceSplitString::Data::~Data()
 {
     if (!m_keyString.isNull())
         sharedDataMap().remove(m_keyString);
 }
 
 PassRefPtr<SpaceSplitString::Data> SpaceSplitString::Data::create(const AtomicString& string)
 {
@@ skipping 19 matching lines @@
 
 SpaceSplitString::Data::Data(const SpaceSplitString::Data& other)
     : RefCounted<Data>()
     , m_vector(other.m_vector)
 {
     // Note that we don't copy m_keyString to indicate to the destructor that there's nothing
     // to be removed from the sharedDataMap().
 }
 
 } // namespace blink