Don't allocate Strings in FontDescription().

Source/platform/fonts/FontDescription.cpp

Index: Source/platform/fonts/FontDescription.cpp
diff --git a/Source/platform/fonts/FontDescription.cpp b/Source/platform/fonts/FontDescription.cpp
index 7a9d0b9b5606b2a5ec65409bef47764fb8e55cbd..85d0035d9ede83e326602953a3484be49e24ed30 100644
--- a/Source/platform/fonts/FontDescription.cpp
+++ b/Source/platform/fonts/FontDescription.cpp
@@ -39,7 +39,7 @@ 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;
@@ -123,6 +123,21 @@ FontDescription::VariantLigatures FontDescription::variantLigatures() const
     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());