Reduce PropertyTreeState construction and copies

third_party/WebKit/Source/core/paint/ObjectPaintProperties.h

 // Copyright 2015 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.
 
 #ifndef ObjectPaintProperties_h
 #define ObjectPaintProperties_h
 
 #include "core/CoreExport.h"
 #include "platform/geometry/LayoutPoint.h"
 #include "platform/graphics/paint/ClipPaintPropertyNode.h"
@@ skipping 116 matching lines @@
   // instead point to the transform space setup by div's ancestors.
   const PropertyTreeState* localBorderBoxProperties() const {
     return m_localBorderBoxProperties.get();
   }
 
   // This is the complete set of property nodes and paint offset that can be
   // used to paint the contents of this object. It is similar to
   // localBorderBoxProperties but includes properties (e.g., overflow clip,
   // scroll translation) that apply to contents. This is suitable for paint
   // invalidation.
-  PropertyTreeState contentsProperties() const;
+  const PropertyTreeState* contentsProperties() const {
+    if (!m_contentsProperties) {
+      if (!m_localBorderBoxProperties)
+        return nullptr;
+      updateContentsProperties();
+    } else {
+#if DCHECK_IS_ON()
+      // Check if the cached m_contentsProperties is valid.
+      DCHECK(m_localBorderBoxProperties);
+      std::unique_ptr<PropertyTreeState> oldProperties =
+          std::move(m_contentsProperties);
+      updateContentsProperties();
+      DCHECK(*m_contentsProperties == *oldProperties);
+#endif
+    }
+    return m_contentsProperties.get();
+  };
 
   void updateLocalBorderBoxProperties(
       const TransformPaintPropertyNode* transform,
       const ClipPaintPropertyNode* clip,
       const EffectPaintPropertyNode* effect,
       const ScrollPaintPropertyNode* scroll) {
     if (m_localBorderBoxProperties) {
       m_localBorderBoxProperties->setTransform(transform);
       m_localBorderBoxProperties->setClip(clip);
       m_localBorderBoxProperties->setEffect(effect);
       m_localBorderBoxProperties->setScroll(scroll);
     } else {
       m_localBorderBoxProperties = WTF::wrapUnique(new PropertyTreeState(
           PropertyTreeState(transform, clip, effect, scroll)));
     }
+    m_contentsProperties = nullptr;
   }
-  void clearLocalBorderBoxProperties() { m_localBorderBoxProperties = nullptr; }
+  void clearLocalBorderBoxProperties() {
+    m_localBorderBoxProperties = nullptr;
+    m_contentsProperties = nullptr;
+  }
 
   // The following clear* functions return true if the property tree structure
   // changes (an existing node was deleted), and false otherwise. See the
   // class-level comment ("update & clear implementation note") for details
   // about why this is needed for efficient updates.
   bool clearPaintOffsetTranslation() { return clear(m_paintOffsetTranslation); }
   bool clearTransform() { return clear(m_transform); }
   bool clearEffect() { return clear(m_effect); }
   bool clearCssClip() { return clear(m_cssClip); }
   bool clearCssClipFixedPosition() { return clear(m_cssClipFixedPosition); }
@@ skipping 125 matching lines @@
   template <typename PaintPropertyNode, typename... Args>
   bool update(RefPtr<PaintPropertyNode>& field, Args&&... args) {
     if (field) {
       field->update(std::forward<Args>(args)...);
       return false;
     }
     field = PaintPropertyNode::create(std::forward<Args>(args)...);
     return true;
   }
 
+  void updateContentsProperties() const;
+
   RefPtr<TransformPaintPropertyNode> m_paintOffsetTranslation;
   RefPtr<TransformPaintPropertyNode> m_transform;
   RefPtr<EffectPaintPropertyNode> m_effect;
   RefPtr<ClipPaintPropertyNode> m_cssClip;
   RefPtr<ClipPaintPropertyNode> m_cssClipFixedPosition;
   RefPtr<ClipPaintPropertyNode> m_innerBorderRadiusClip;
   RefPtr<ClipPaintPropertyNode> m_overflowClip;
   RefPtr<TransformPaintPropertyNode> m_perspective;
   // TODO(pdr): Only LayoutSVGRoot needs this and it should be moved there.
   RefPtr<TransformPaintPropertyNode> m_svgLocalToBorderBoxTransform;
   RefPtr<TransformPaintPropertyNode> m_scrollTranslation;
   RefPtr<TransformPaintPropertyNode> m_scrollbarPaintOffset;
   RefPtr<ScrollPaintPropertyNode> m_scroll;
 
   std::unique_ptr<PropertyTreeState> m_localBorderBoxProperties;
+  mutable std::unique_ptr<PropertyTreeState> m_contentsProperties;
 };
 
 }  // namespace blink
 
 #endif  // ObjectPaintProperties_h