Don't allocate Strings in FontDescription().

Source/platform/fonts/FontDescription.cpp

 /*
  * Copyright (C) 2007 Nicholas Shanks <contact@nickshanks.com>
  * Copyright (C) 2008 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 21 matching lines @@
 
 #include "platform/RuntimeEnabledFeatures.h"
 #include "wtf/text/AtomicStringHash.h"
 #include "wtf/text/StringHash.h"
 
 namespace blink {
 
 struct SameSizeAsFontDescription {
     FontFamily familyList;
     RefPtr<FontFeatureSettings> m_featureSettings;
-    String locale;
+    AtomicString locale;
     float sizes[4];
     // FXIME: Make them fit into one word.
     uint32_t bitfields;
     uint32_t bitfields2 : 7;
 };
 
 static_assert(sizeof(FontDescription) == sizeof(SameSizeAsFontDescription), "FontDescription should stay small");
 
 TypesettingFeatures FontDescription::s_defaultTypesettingFeatures = 0;
 
@@ skipping 63 matching lines @@
     VariantLigatures ligatures;
 
     ligatures.common = commonLigaturesState();
     ligatures.discretionary = discretionaryLigaturesState();
     ligatures.historical = historicalLigaturesState();
     ligatures.contextual = contextualLigaturesState();
 
     return ligatures;
 }
 
+static const AtomicString& defaultLocale()
+{
+    DEFINE_STATIC_LOCAL(AtomicString, locale, ());
+    if (locale.isNull())
+        locale = AtomicString("en");
+    return locale;
+}
+
+const AtomicString& FontDescription::locale() const
+{
+    if (m_locale.isNull())
+        return defaultLocale();
+    return m_locale;
+}
+
 void FontDescription::setTraits(FontTraits traits)
 {
     setStyle(traits.style());
     setVariant(traits.variant());
     setWeight(traits.weight());
     setStretch(traits.stretch());
 }
 
 void FontDescription::setVariantLigatures(const VariantLigatures& ligatures)
 {
@@ skipping 82 matching lines @@
 
         if (discretionaryLigaturesState() == FontDescription::EnabledLigaturesState
             || historicalLigaturesState() == FontDescription::EnabledLigaturesState
             || contextualLigaturesState() == FontDescription::EnabledLigaturesState) {
             m_typesettingFeatures |= blink::Ligatures;
         }
     }
 }
 
 } // namespace blink