Force subtree paint property updates on local border box changes

third_party/WebKit/Source/platform/graphics/paint/PropertyTreeState.h

 // Copyright 2016 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 PropertyTreeState_h
 #define PropertyTreeState_h
 
 #include "platform/graphics/paint/ClipPaintPropertyNode.h"
 #include "platform/graphics/paint/EffectPaintPropertyNode.h"
 #include "platform/graphics/paint/ScrollPaintPropertyNode.h"
 #include "platform/graphics/paint/TransformPaintPropertyNode.h"
 #include "wtf/HashFunctions.h"
 #include "wtf/HashTraits.h"
 
 namespace blink {
 
 // A complete set of paint properties including those that are inherited from
-// other objects.  RefPtrs are used to guard against use-after-free bugs and
-// DCHECKs ensure PropertyTreeState never retains the last reference to a
-// property tree node.
+// other objects. RefPtrs are only used to guard against use-after-free bugs.
 class PropertyTreeState {
  public:
   PropertyTreeState(const TransformPaintPropertyNode* transform,
                     const ClipPaintPropertyNode* clip,
                     const EffectPaintPropertyNode* effect,
                     const ScrollPaintPropertyNode* scroll)
       : m_transform(transform),
         m_clip(clip),
         m_effect(effect),
         m_scroll(scroll) {
     DCHECK(!m_transform || !m_transform->hasOneRef());
     DCHECK(!m_clip || !m_clip->hasOneRef());
     DCHECK(!m_effect || !m_effect->hasOneRef());
     DCHECK(!m_scroll || !m_scroll->hasOneRef());
   }
 
   const TransformPaintPropertyNode* transform() const {
-    DCHECK(!m_transform || !m_transform->hasOneRef());
     return m_transform.get();
   }
   void setTransform(const TransformPaintPropertyNode* node) {
     m_transform = node;
     DCHECK(!node->hasOneRef());
   }
 
   const ClipPaintPropertyNode* clip() const {
-    DCHECK(!m_clip || !m_clip->hasOneRef());
     return m_clip.get();
   }
   void setClip(const ClipPaintPropertyNode* node) {
     m_clip = node;
     DCHECK(!node->hasOneRef());
   }
 
   const EffectPaintPropertyNode* effect() const {
-    DCHECK(!m_effect || !m_effect->hasOneRef());
     return m_effect.get();
   }
   void setEffect(const EffectPaintPropertyNode* node) {
     m_effect = node;
     DCHECK(!node->hasOneRef());
   }
 
   const ScrollPaintPropertyNode* scroll() const {
-    DCHECK(!m_scroll || !m_scroll->hasOneRef());
     return m_scroll.get();
   }
   void setScroll(const ScrollPaintPropertyNode* node) {
     m_scroll = node;
     DCHECK(!node->hasOneRef());
   }
 
  private:
   RefPtr<const TransformPaintPropertyNode> m_transform;
   RefPtr<const ClipPaintPropertyNode> m_clip;
   RefPtr<const EffectPaintPropertyNode> m_effect;
   RefPtr<const ScrollPaintPropertyNode> m_scroll;
 };
 
 inline bool operator==(const PropertyTreeState& a, const PropertyTreeState& b) {
   return a.transform() == b.transform() && a.clip() == b.clip() &&
          a.effect() == b.effect() && a.scroll() == b.scroll();
 }
 
 }  // namespace blink
 
 #endif  // PropertyTreeState_h