Reuse existing paint property node is possible

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

Index: third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.h
diff --git a/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.h b/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.h
index 16f07086d7c79ffe1a76b6eefae797928862a7c9..a1d60a1e2f09a74a8cf6b9e4d306470424921efe 100644
--- a/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.h
+++ b/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.h
@@ -15,6 +15,7 @@ namespace blink {
 
 class FrameView;
 class LayoutObject;
+class ObjectPaintProperties;
 
 // The context for PaintPropertyTreeBuilder.
 // It's responsible for bookkeeping tree state in other order, for example, the most recent
@@ -67,16 +68,48 @@ public:
     void buildTreeNodes(const LayoutObject&, PaintPropertyTreeBuilderContext&);
 
 private:
+    // Common logic to update a paint property. It tries to reuse the existing paint property node of
+    // the object if the value is not changed. Returns the existing or newly created paint property node,
+    // or nullptr if no paint property node is needed.
+    // It requires a ComputeProperty function which computes the paint property node value if needed and
+    // returns true, or returns false if no paint property node value is needed.
+    template <
+        typename PropertyNode,
+        PropertyNode* (ObjectPaintProperties::*Getter)() const,
+        void (ObjectPaintProperties::*Setter)(PassRefPtr<PropertyNode>),
+        bool (*ComputeProperty)(const LayoutObject&, PaintPropertyTreeBuilderContext&, typename PropertyNode::Value&)>
+    static PropertyNode* updateObjectPaintProperty(const LayoutObject&, PaintPropertyTreeBuilderContext&, PropertyNode*& contextProperty);
+
+    static bool computePaintOffsetTranslation(const LayoutObject&, PaintPropertyTreeBuilderContext&, TransformPaintPropertyNode::Value&);
     static void updatePaintOffsetTranslation(const LayoutObject&, PaintPropertyTreeBuilderContext&);
+
+    static bool computeTransform(const LayoutObject&, PaintPropertyTreeBuilderContext&, TransformPaintPropertyNode::Value&);
     static void updateTransform(const LayoutObject&, PaintPropertyTreeBuilderContext&);
+
+    static bool computeEffect(const LayoutObject&, PaintPropertyTreeBuilderContext&, EffectPaintPropertyNode::Value&);
     static void updateEffect(const LayoutObject&, PaintPropertyTreeBuilderContext&);
+
+    static bool computeCssClip(const LayoutObject&, PaintPropertyTreeBuilderContext&, ClipPaintPropertyNode::Value&);
     static void updateCssClip(const LayoutObject&, PaintPropertyTreeBuilderContext&);
+
     static void updateLocalBorderBoxContext(const LayoutObject&, const PaintPropertyTreeBuilderContext&);
+
+    static bool computeScrollbarPaintOffset(const LayoutObject&, const PaintPropertyTreeBuilderContext&, TransformPaintPropertyNode::Value&);
     static void updateScrollbarPaintOffset(const LayoutObject&, const PaintPropertyTreeBuilderContext&);
+
+    static bool computeOverflowClip(const LayoutObject&, PaintPropertyTreeBuilderContext&, ClipPaintPropertyNode::Value&);
     static void updateOverflowClip(const LayoutObject&, PaintPropertyTreeBuilderContext&);
+
+    static bool computePerspective(const LayoutObject&, PaintPropertyTreeBuilderContext&, TransformPaintPropertyNode::Value&);
     static void updatePerspective(const LayoutObject&, PaintPropertyTreeBuilderContext&);
+
+    static bool computeSvgLocalToBorderBoxTransform(const LayoutObject&, PaintPropertyTreeBuilderContext&, TransformPaintPropertyNode::Value&);
     static void updateSvgLocalToBorderBoxTransform(const LayoutObject&, PaintPropertyTreeBuilderContext&);
+
+    static bool computeScrollTranslation(const LayoutObject&, PaintPropertyTreeBuilderContext&, TransformPaintPropertyNode::Value&);
     static void updateScrollTranslation(const LayoutObject&, PaintPropertyTreeBuilderContext&);
+
+    static bool computeOutOfFlowContext(const LayoutObject&, PaintPropertyTreeBuilderContext&, ClipPaintPropertyNode::Value&);
     static void updateOutOfFlowContext(const LayoutObject&, PaintPropertyTreeBuilderContext&);
 };