Add LayoutObject::RarePaintData for rare paint data

third_party/WebKit/Source/core/layout/LayoutObject.h

 /*
  * Copyright (C) 2000 Lars Knoll (knoll@kde.org)
  *           (C) 2000 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  *           (C) 2004 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2012 Apple Inc.
  *               All rights reserved.
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 376 matching lines @@
   }
   virtual void removeChild(LayoutObject*);
   virtual bool createsAnonymousWrapper() const { return false; }
   //////////////////////////////////////////
 
   // Sets the parent of this object but doesn't add it as a child of the parent.
   void setDangerousOneWayParent(LayoutObject*);
 
   // For SlimmingPaintInvalidation/SPv2 only.
   // The ObjectPaintProperties structure holds references to the property tree
-  // nodes that are created by the layout object for painting. The property
-  // nodes are only updated during InPrePaint phase of the document lifecycle
-  // and shall remain immutable during other phases.
-  const ObjectPaintProperties* paintProperties() const;
+  // nodes that are created by the layout object. The property nodes should only
+  // be updated during InPrePaint phase of the document lifecycle.
+  const ObjectPaintProperties* paintProperties() const {
+    DCHECK(RuntimeEnabledFeatures::slimmingPaintInvalidationEnabled());
+    return m_rarePaintData ? m_rarePaintData->paintProperties() : nullptr;
+  }
 
  private:
-  ObjectPaintProperties& ensurePaintProperties();
+  // This is for paint-related data that is not needed on all LayoutObjects.
+  // TODO(pdr): Store LayoutBoxModelObject's m_paintLayer in this structure.
+  // TODO(pdr): Store ObjectPaintProperties::LocalBorderBoxProperties here.
+  struct CORE_EXPORT RarePaintData {

[Xianzhu, 2017/03/30 03:11:18]

Nit: This data structure seems like a class more than a struct.

[pdr., 2017/03/30 18:57:33]

Sure, done.

+    WTF_MAKE_NONCOPYABLE(RarePaintData);
+    USING_FAST_MALLOC(RarePaintData);
+
+   public:
+    RarePaintData();
+    ~RarePaintData();
+
+    ObjectPaintProperties* paintProperties() const {
+      return m_paintProperties.get();
+    }
+    ObjectPaintProperties& ensurePaintProperties();
+
+   private:
+    // Holds references to the paint property nodes created by this object.
+    std::unique_ptr<ObjectPaintProperties> m_paintProperties;
+  };
+
+  RarePaintData& ensureRarePaintData();
+  RarePaintData* rarePaintData() { return m_rarePaintData.get(); }
 
   //////////////////////////////////////////
   // Helper functions. Dangerous to use!
   void setPreviousSibling(LayoutObject* previous) { m_previous = previous; }
   void setNextSibling(LayoutObject* next) { m_next = next; }
   void setParent(LayoutObject* parent) {
     m_parent = parent;
 
     // Only update if our flow thread state is different from our new parent and
     // if we're not a LayoutFlowThread.
@@ skipping 1359 matching lines @@
    protected:
     friend class PaintPropertyTreeBuilder;
     FRIEND_TEST_ALL_PREFIXES(AnimationCompositorAnimationsTest,
                              canStartAnimationOnCompositorTransformSPv2);
     FRIEND_TEST_ALL_PREFIXES(AnimationCompositorAnimationsTest,
                              canStartAnimationOnCompositorEffectSPv2);
 
     // The following two functions can be called from PaintPropertyTreeBuilder
     // only.
     ObjectPaintProperties& ensurePaintProperties() {
-      return m_layoutObject.ensurePaintProperties();
+      return m_layoutObject.ensureRarePaintData().ensurePaintProperties();
     }
     ObjectPaintProperties* paintProperties() {
-      return const_cast<ObjectPaintProperties*>(
-          m_layoutObject.paintProperties());
+      if (auto* paintData = m_layoutObject.rarePaintData())
+        return paintData->paintProperties();
+      return nullptr;
     }
 
     friend class LayoutObject;
     MutableForPainting(const LayoutObject& layoutObject)
         : m_layoutObject(const_cast<LayoutObject&>(layoutObject)) {}
 
     LayoutObject& m_layoutObject;
   };
   MutableForPainting getMutableForPainting() const {
     return MutableForPainting(*this);
@@ skipping 751 matching lines @@
   // adjustVisualRectForCompositedScrolling().
   LayoutRect m_visualRect;
 
   // This stores the paint offset computed by the latest paint property tree
   // building. It is relative to the containing transform space. It is the same
   // offset that will be used to paint the object on SPv2. It's used to detect
   // paint offset change for paint invalidation on SPv2, and partial paint
   // property tree update for SlimmingPaintInvalidation on SPv1 and SPv2.
   LayoutPoint m_paintOffset;
 
-  // For SPv2 only. The ObjectPaintProperties structure holds references to the
-  // property tree nodes that are created by the layout object for painting.
-  std::unique_ptr<ObjectPaintProperties> m_paintProperties;
+  std::unique_ptr<RarePaintData> m_rarePaintData;
 };
 
 // FIXME: remove this once the layout object lifecycle ASSERTS are no longer
 // hit.
 class DeprecatedDisableModifyLayoutTreeStructureAsserts {
   STACK_ALLOCATED();
   WTF_MAKE_NONCOPYABLE(DeprecatedDisableModifyLayoutTreeStructureAsserts);
 
  public:
   DeprecatedDisableModifyLayoutTreeStructureAsserts();
@@ skipping 207 matching lines @@
 CORE_EXPORT void showLineTree(const blink::LayoutObject*);
 CORE_EXPORT void showLayoutTree(const blink::LayoutObject* object1);
 // We don't make object2 an optional parameter so that showLayoutTree
 // can be called from gdb easily.
 CORE_EXPORT void showLayoutTree(const blink::LayoutObject* object1,
                                 const blink::LayoutObject* object2);
 
 #endif
 
 #endif  // LayoutObject_h