Alternate approach to updating paint property nodes

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

Index: third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.cpp
diff --git a/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.cpp b/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.cpp
index 1d394cb7cd37438feba099574ccad966af718cfb..fe5ca0904071d00687661588c673a34747f3e94c 100644
--- a/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.cpp
@@ -106,6 +106,25 @@ static FloatPoint3D transformOrigin(const LayoutBox& box)
         style.transformOriginZ());
 }
 
+void PaintPropertyTreeBuilder::clearTransformProperty(const LayoutObject& object, void (ObjectPaintProperties::*setter)(PassRefPtr<TransformPaintPropertyNode>))
+{
+    if (ObjectPaintProperties* existingProperties = object.objectPaintProperties())
+        (existingProperties->*setter)(nullptr);
+}
+
+void PaintPropertyTreeBuilder::updateOrCreateTransformProperty(const LayoutObject& object, TransformPaintPropertyNode* (ObjectPaintProperties::*getter)() const, void (ObjectPaintProperties::*setter)(PassRefPtr<TransformPaintPropertyNode>), const TransformationMatrix& matrix, const FloatPoint3D& origin, PassRefPtr<TransformPaintPropertyNode> parent)
+{
+    ObjectPaintProperties* existingProperties = object.objectPaintProperties();
+    TransformPaintPropertyNode* existingTransform = existingProperties ? (existingProperties->*getter)() : nullptr;
+    if (!existingTransform) {

[pdr., 2016/07/21 23:14:01]

Oops, you'll want to do a comparison of the values here too. Something like:
if (!existingTransform || existingTransform->matrix() != matrix ||
existingTransform->origin() != origin)

+        (object.getMutableForPainting().ensureObjectPaintProperties().*setter)(TransformPaintPropertyNode::create(matrix, origin, parent));
+        return;
+    }
+    existingTransform->setMatrix(matrix);
+    existingTransform->setOrigin(origin);
+    existingTransform->setParent(parent);
+}
+
 void PaintPropertyTreeBuilder::updateTransform(const LayoutObject& object, PaintPropertyTreeBuilderContext& context)
 {
     if (object.isSVG() && !object.isSVGRoot()) {
@@ -117,28 +136,28 @@ void PaintPropertyTreeBuilder::updateTransform(const LayoutObject& object, Paint
         // the animation passes through the identity matrix.
         // FIXME(pdr): Refactor this so all non-root SVG objects use the same transform function.
         const AffineTransform& transform = object.isSVGForeignObject() ? object.localSVGTransform() : object.localToSVGParentTransform();
-        if (transform.isIdentity())
+        if (transform.isIdentity()) {
+            clearTransformProperty(object, &ObjectPaintProperties::setTransform);
             return;
+        }
 
         // The origin is included in the local transform, so use an empty origin.
-        RefPtr<TransformPaintPropertyNode> svgTransform = TransformPaintPropertyNode::create(
-            transform, FloatPoint3D(0, 0, 0), context.current.transform);
-        context.current.transform = svgTransform.get();
-        object.getMutableForPainting().ensureObjectPaintProperties().setTransform(svgTransform.release());
+        updateOrCreateTransformProperty(object, &ObjectPaintProperties::transform, &ObjectPaintProperties::setTransform, transform, FloatPoint3D(0, 0, 0), context.current.transform);
+        context.current.transform = object.objectPaintProperties()->transform();
         return;
     }
 
     const ComputedStyle& style = object.styleRef();
-    if (!object.isBox() || !style.hasTransform())
+    if (!object.isBox() || !style.hasTransform()) {
+        clearTransformProperty(object, &ObjectPaintProperties::setTransform);
         return;
+    }
 
     TransformationMatrix matrix;
     style.applyTransform(matrix, toLayoutBox(object).size(), ComputedStyle::ExcludeTransformOrigin,
         ComputedStyle::IncludeMotionPath, ComputedStyle::IncludeIndependentTransformProperties);
-    RefPtr<TransformPaintPropertyNode> transformNode = TransformPaintPropertyNode::create(
-        matrix, transformOrigin(toLayoutBox(object)), context.current.transform);
-    context.current.transform = transformNode.get();
-    object.getMutableForPainting().ensureObjectPaintProperties().setTransform(transformNode.release());
+    updateOrCreateTransformProperty(object, &ObjectPaintProperties::transform, &ObjectPaintProperties::setTransform, matrix, transformOrigin(toLayoutBox(object)), context.current.transform);
+    context.current.transform = object.objectPaintProperties()->transform();
 }
 
 void PaintPropertyTreeBuilder::updateEffect(const LayoutObject& object, PaintPropertyTreeBuilderContext& context)
@@ -385,8 +404,6 @@ static void deriveBorderBoxFromContainerContext(const LayoutObject& object, Pain
 
 void PaintPropertyTreeBuilder::buildTreeNodes(const LayoutObject& object, PaintPropertyTreeBuilderContext& context)
 {
-    object.getMutableForPainting().clearObjectPaintProperties();
-
     if (!object.isBoxModelObject() && !object.isSVG())
         return;