Reduce the number of CachedUAStyles

Source/core/css/resolver/StyleResolverState.h

Index: Source/core/css/resolver/StyleResolverState.h
diff --git a/Source/core/css/resolver/StyleResolverState.h b/Source/core/css/resolver/StyleResolverState.h
index ae3d449711839c157eb5a9e4a7786ff3a477efa9..2a723ba471b0b802d0a3928aa6daa59073cae1df 100644
--- a/Source/core/css/resolver/StyleResolverState.h
+++ b/Source/core/css/resolver/StyleResolverState.h
@@ -100,9 +100,14 @@ public:
         // and constructing it is expensive so we avoid it if possible.
         if (!style()->hasAppearance())
             return;
-        m_cachedUAStyle = CachedUAStyle(style());
+
+        m_cachedUAStyle = CachedUAStyle::create(style());
+    }
+
+    const CachedUAStyle* cachedUAStyle() const
+    {
+        return m_cachedUAStyle.get();
     }
-    const CachedUAStyle& cachedUAStyle() const { return m_cachedUAStyle; }
 
     ElementStyleResources& elementStyleResources() { return m_elementStyleResources; }
     const CSSToStyleMap& styleMap() const { return m_styleMap; }
@@ -150,7 +155,7 @@ private:
 
     FontBuilder m_fontBuilder;
 
-    CachedUAStyle m_cachedUAStyle;
+    OwnPtr<CachedUAStyle> m_cachedUAStyle;
 
     ElementStyleResources m_elementStyleResources;
     // CSSToStyleMap is a pure-logic class and only contains