Implement incremental paint property tree rebuilding

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

 // 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.
 
 #include "core/paint/PaintPropertyTreeBuilder.h"
 
 #include "core/frame/FrameView.h"
 #include "core/frame/LocalFrame.h"
 #include "core/frame/Settings.h"
 #include "core/layout/LayoutInline.h"
 #include "core/layout/LayoutPart.h"
 #include "core/layout/LayoutView.h"
 #include "core/layout/svg/LayoutSVGRoot.h"
 #include "core/paint/ObjectPaintProperties.h"
 #include "core/paint/PaintLayer.h"
+#include "core/paint/PaintPropertyUnderInvalidationChecks.h"
 #include "core/paint/SVGRootPainter.h"
 #include "platform/transforms/TransformationMatrix.h"
 #include "wtf/PtrUtil.h"
 #include <memory>
 
 namespace blink {
 
 namespace {
 TransformPaintPropertyNode* rootTransformNode() {
   DEFINE_STATIC_REF(TransformPaintPropertyNode, rootTransform,
@@ skipping 102 matching lines @@
     existingScroll->update(std::move(parent), std::move(scrollOffset), clip,
                            bounds, userScrollableHorizontal,
                            userScrollableVertical);
   else
     frameView.setScroll(ScrollPaintPropertyNode::create(
         std::move(parent), std::move(scrollOffset), clip, bounds,
         userScrollableHorizontal, userScrollableVertical));
   return frameView.scroll();
 }
 
-void PaintPropertyTreeBuilder::buildTreeNodes(
+void PaintPropertyTreeBuilder::updateProperties(
     FrameView& frameView,
     PaintPropertyTreeBuilderContext& context) {
   if (RuntimeEnabledFeatures::rootLayerScrollingEnabled()) {
     LayoutView* layoutView = frameView.layoutView();
     if (!layoutView)
       return;
 
-    TransformationMatrix frameTranslate;
-    frameTranslate.translate(frameView.x() + layoutView->location().x() +
-                                 context.current.paintOffset.x(),
-                             frameView.y() + layoutView->location().y() +
-                                 context.current.paintOffset.y());
-    context.current.transform =
-        layoutView->getMutableForPainting()
-            .ensurePaintProperties()
-            .updatePaintOffsetTranslation(context.current.transform,
-                                          frameTranslate, FloatPoint3D());
+#ifndef NDEBUG

[chrishtr, 2016/10/21 22:03:09]

#if DCHECK_IS_ON

[pdr., 2016/10/26 03:10:48]

Done

+    auto underInvalidationChecker =
+        ObjectUnderInvalidationCheckScope::createIfNeeded(*layoutView);
+#endif
+
+    if (layoutView->paintPropertiesValid()) {
+      // No invalidation so update the context using existing properties.
+      const auto* properties = layoutView->paintProperties();
+      if (properties && properties->paintOffsetTranslation())

[chrishtr, 2016/10/21 22:03:09]

This conditional is not needed, and therefore line 156 and 163 can be combined
into a single line at 169.

It appears you can do the same kind of thing in some/most of the other sites, so
the general code structure would
be:

if (!paintPropertiesValid) {
  update the property tree nodes
}

unconditionally update the context.

[pdr., 2016/10/26 03:10:48]

This approach is very nice.

Done.

+        context.current.transform = properties->paintOffsetTranslation();
+    } else {
+      TransformationMatrix frameTranslate;
+      frameTranslate.translate(frameView.x() + layoutView->location().x() +
+                                   context.current.paintOffset.x(),
+                               frameView.y() + layoutView->location().y() +
+                                   context.current.paintOffset.y());
+      context.current.transform =
+          layoutView->getMutableForPainting()
+              .ensurePaintProperties()
+              .updatePaintOffsetTranslation(context.current.transform,
+                                            frameTranslate, FloatPoint3D());
+    }
     context.current.paintOffset = LayoutPoint();
     context.current.renderingContextID = 0;
     context.current.shouldFlattenInheritedTransform = true;
     context.absolutePosition = context.current;
     context.containerForAbsolutePosition =
         nullptr;  // This will get set in updateOutOfFlowContext().
     context.fixedPosition = context.current;
     return;
   }
 
-  TransformationMatrix frameTranslate;
-  frameTranslate.translate(frameView.x() + context.current.paintOffset.x(),
-                           frameView.y() + context.current.paintOffset.y());
-  context.current.transform = updateFrameViewPreTranslation(
-      frameView, context.current.transform, frameTranslate, FloatPoint3D());
+#ifndef NDEBUG
+  auto underInvalidationChecker =
+      FrameViewUnderInvalidationCheckScope::createIfNeeded(&frameView);
+#endif
 
-  FloatRoundedRect contentClip(
-      IntRect(IntPoint(), frameView.visibleContentSize()));
-  context.current.clip = updateFrameViewContentClip(
-      frameView, context.current.clip, frameView.preTranslation(), contentClip);
+  const auto* initialTransformNode = context.current.transform;
+  auto* initialScrollNode = context.current.scroll;
 
-  // Record the fixed properties before any scrolling occurs.
-  const auto* fixedTransformNode = context.current.transform;
-  auto* fixedScrollNode = context.current.scroll;
+  if (frameView.paintPropertiesValid()) {
+    // No invalidation so update the context using existing properties.
+    if (const auto* preTranslation = frameView.preTranslation())
+      context.current.transform = preTranslation;
+    if (const auto* clip = frameView.contentClip())
+      context.current.clip = clip;
+    if (const auto* scrollTranslation = frameView.scrollTranslation())
+      context.current.transform = scrollTranslation;
+    if (auto* scroll = frameView.scroll())
+      context.current.scroll = scroll;
+  } else {
+    TransformationMatrix frameTranslate;
+    frameTranslate.translate(frameView.x() + context.current.paintOffset.x(),
+                             frameView.y() + context.current.paintOffset.y());
+    context.current.transform = updateFrameViewPreTranslation(
+        frameView, context.current.transform, frameTranslate, FloatPoint3D());
 
-  ScrollOffset scrollOffset = frameView.scrollOffset();
-  if (frameView.isScrollable() || !scrollOffset.isZero()) {
-    TransformationMatrix frameScroll;
-    frameScroll.translate(-scrollOffset.width(), -scrollOffset.height());
-    context.current.transform = updateFrameViewScrollTranslation(
-        frameView, frameView.preTranslation(), frameScroll, FloatPoint3D());
+    FloatRoundedRect contentClip(
+        IntRect(IntPoint(), frameView.visibleContentSize()));
+    context.current.clip =
+        updateFrameViewContentClip(frameView, context.current.clip,
+                                   frameView.preTranslation(), contentClip);
 
-    IntSize scrollClip = frameView.visibleContentSize();
-    IntSize scrollBounds = frameView.contentsSize();
-    bool userScrollableHorizontal =
-        frameView.userInputScrollable(HorizontalScrollbar);
-    bool userScrollableVertical =
-        frameView.userInputScrollable(VerticalScrollbar);
-    context.current.scroll = updateFrameViewScroll(
-        frameView, context.current.scroll, frameView.scrollTranslation(),
-        scrollClip, scrollBounds, userScrollableHorizontal,
-        userScrollableVertical);
-  } else {
-    // Ensure pre-existing properties are cleared when there is no scrolling.
-    frameView.setScrollTranslation(nullptr);
-    frameView.setScroll(nullptr);
+    ScrollOffset scrollOffset = frameView.scrollOffset();
+    if (frameView.isScrollable() || !scrollOffset.isZero()) {
+      TransformationMatrix frameScroll;
+      frameScroll.translate(-scrollOffset.width(), -scrollOffset.height());
+      context.current.transform = updateFrameViewScrollTranslation(
+          frameView, frameView.preTranslation(), frameScroll, FloatPoint3D());
+
+      IntSize scrollClip = frameView.visibleContentSize();
+      IntSize scrollBounds = frameView.contentsSize();
+      bool userScrollableHorizontal =
+          frameView.userInputScrollable(HorizontalScrollbar);
+      bool userScrollableVertical =
+          frameView.userInputScrollable(VerticalScrollbar);
+      context.current.scroll = updateFrameViewScroll(
+          frameView, context.current.scroll, frameView.scrollTranslation(),
+          scrollClip, scrollBounds, userScrollableHorizontal,
+          userScrollableVertical);
+    } else {
+      // Ensure pre-existing properties are cleared when there is no scrolling.
+      frameView.setScrollTranslation(nullptr);
+      frameView.setScroll(nullptr);
+    }
   }
 
   // Initialize the context for current, absolute and fixed position cases.
   // They are the same, except that scroll translation does not apply to
   // fixed position descendants.
   context.current.paintOffset = LayoutPoint();
   context.current.renderingContextID = 0;
   context.current.shouldFlattenInheritedTransform = true;
   context.absolutePosition = context.current;
   context.containerForAbsolutePosition = nullptr;
   context.fixedPosition = context.current;
-  context.fixedPosition.transform = fixedTransformNode;
-  context.fixedPosition.scroll = fixedScrollNode;
+  context.fixedPosition.transform = frameView.preTranslation()
+                                        ? frameView.preTranslation()
+                                        : initialTransformNode;
+  context.fixedPosition.scroll = initialScrollNode;
 
   std::unique_ptr<PropertyTreeState> contentsState(
       new PropertyTreeState(context.current.transform, context.current.clip,
                             context.currentEffect, context.current.scroll));
   frameView.setTotalPropertyTreeStateForContents(std::move(contentsState));
 }
 
 void PaintPropertyTreeBuilder::updatePaintOffsetTranslation(
     const LayoutObject& object,
     PaintPropertyTreeBuilderContext& context) {
   if (object.isBoxModelObject() &&
       context.current.paintOffset != LayoutPoint()) {
     // TODO(trchen): Eliminate PaintLayer dependency.
     PaintLayer* layer = toLayoutBoxModelObject(object).layer();
     if (layer && layer->paintsWithTransform(GlobalPaintNormalPhase)) {
       // We should use the same subpixel paint offset values for snapping
       // regardless of whether a transform is present. If there is a transform
       // we round the paint offset but keep around the residual fractional
       // component for the transformed content to paint with.  In spv1 this was
       // called "subpixel accumulation". For more information, see
       // PaintLayer::subpixelAccumulation() and
       // PaintLayerPainter::paintFragmentByApplyingTransform.
       IntPoint roundedPaintOffset =
           roundedIntPoint(context.current.paintOffset);
       LayoutPoint fractionalPaintOffset =
           LayoutPoint(context.current.paintOffset - roundedPaintOffset);
 
-      context.current.transform =
-          object.getMutableForPainting()
-              .ensurePaintProperties()
-              .updatePaintOffsetTranslation(
-                  context.current.transform,
-                  TransformationMatrix().translate(roundedPaintOffset.x(),
-                                                   roundedPaintOffset.y()),
-                  FloatPoint3D(),
-                  context.current.shouldFlattenInheritedTransform,
-                  context.current.renderingContextID);
+      // TODO(pdr): Refactor this check to be higher so the layer and
+      // paintsWithTransform checks can be skipped if there's no invalidation.
+      if (object.paintPropertiesValid()) {
+        // No invalidation so update the context using existing properties.
+        const auto* properties = object.paintProperties();
+        if (properties && properties->paintOffsetTranslation())
+          context.current.transform = properties->paintOffsetTranslation();
+      } else {
+        context.current.transform =
+            object.getMutableForPainting()
+                .ensurePaintProperties()
+                .updatePaintOffsetTranslation(
+                    context.current.transform,
+                    TransformationMatrix().translate(roundedPaintOffset.x(),
+                                                     roundedPaintOffset.y()),
+                    FloatPoint3D(),
+                    context.current.shouldFlattenInheritedTransform,
+                    context.current.renderingContextID);
+      }
       context.current.paintOffset = fractionalPaintOffset;
       return;
     }
   }
 
   if (object.isLayoutView())
     return;
 
-  if (auto* properties = object.getMutableForPainting().paintProperties())
-    properties->clearPaintOffsetTranslation();
+  if (!object.paintPropertiesValid()) {
+    if (auto* properties = object.getMutableForPainting().paintProperties())
+      properties->clearPaintOffsetTranslation();
+  }
 }
 
 static FloatPoint3D transformOrigin(const LayoutBox& box) {

[chrishtr, 2016/10/21 22:03:09]

This method is now getting very long, refactor it?

[pdr., 2016/10/26 03:10:48]

Done. Split out the svg-specific code into its own function.

   const ComputedStyle& style = box.styleRef();
   FloatSize borderBoxSize(box.size());
   return FloatPoint3D(
       floatValueForLength(style.transformOriginX(), borderBoxSize.width()),
       floatValueForLength(style.transformOriginY(), borderBoxSize.height()),
       style.transformOriginZ());
 }
 
 void PaintPropertyTreeBuilder::updateTransform(
     const LayoutObject& object,
     PaintPropertyTreeBuilderContext& context) {
   if (object.isSVG() && !object.isSVGRoot()) {
     // SVG (other than SVGForeignObject) does not use paint offset internally.
     DCHECK(object.isSVGForeignObject() ||
            context.current.paintOffset == LayoutPoint());
 
-    // FIXME(pdr): Check for the presence of a transform instead of the value.
-    // Checking for an identity matrix will cause the property tree structure to
-    // change during animations if 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()) {
-      // The origin is included in the local transform, so leave origin empty.
-      context.current.transform =
-          object.getMutableForPainting()
-              .ensurePaintProperties()
-              .updateTransform(context.current.transform,
-                               TransformationMatrix(transform), FloatPoint3D());
-      context.current.renderingContextID = 0;
-      context.current.shouldFlattenInheritedTransform = false;
-      return;
+    if (object.paintPropertiesValid()) {
+      // No invalidation so update the context using existing properties.
+      if (object.paintProperties() && object.paintProperties()->transform()) {
+        context.current.transform = object.paintProperties()->transform();
+        context.current.shouldFlattenInheritedTransform = false;
+        context.current.renderingContextID = 0;
+      }
+    } else {
+      // FIXME(pdr): Check for the presence of a transform instead of the value.
+      // Checking for an identity matrix will cause the property tree structure
+      // to change during animations if 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()) {
+        // The origin is included in the local transform, so leave origin empty.
+        context.current.transform =
+            object.getMutableForPainting()
+                .ensurePaintProperties()
+                .updateTransform(context.current.transform,
+                                 TransformationMatrix(transform),
+                                 FloatPoint3D());
+        context.current.shouldFlattenInheritedTransform = false;
+        context.current.renderingContextID = 0;
+      } else {
+        if (auto* properties = object.getMutableForPainting().paintProperties())
+          properties->clearTransform();
+      }
     }
-  } else {
-    const ComputedStyle& style = object.styleRef();
-    if (object.isBox() && (style.hasTransform() || style.preserves3D())) {
+    return;
+  }
+
+  const ComputedStyle& style = object.styleRef();
+  if (object.isBox() && (style.hasTransform() || style.preserves3D())) {
+    unsigned renderingContextID = context.current.renderingContextID;
+    unsigned renderingContextIDForChildren = 0;
+    bool flattensInheritedTransform =
+        context.current.shouldFlattenInheritedTransform;
+    bool childrenFlattenInheritedTransform = true;
+
+    // TODO(trchen): transform-style should only be respected if a PaintLayer
+    // is created.
+    if (style.preserves3D()) {
+      // If a node with transform-style: preserve-3d does not exist in an
+      // existing rendering context, it establishes a new one.
+      if (!renderingContextID)
+        renderingContextID = PtrHash<const LayoutObject>::hash(&object);
+      renderingContextIDForChildren = renderingContextID;
+      childrenFlattenInheritedTransform = false;
+    }
+    context.current.renderingContextID = renderingContextIDForChildren;
+    context.current.shouldFlattenInheritedTransform =
+        childrenFlattenInheritedTransform;
+
+    if (object.paintPropertiesValid()) {
+      // No invalidation so update the context using existing properties.
+      if (object.paintProperties() && object.paintProperties()->transform())
+        context.current.transform = object.paintProperties()->transform();
+    } else {
       TransformationMatrix matrix;
       style.applyTransform(
           matrix, toLayoutBox(object).size(),
           ComputedStyle::ExcludeTransformOrigin,
           ComputedStyle::IncludeMotionPath,
           ComputedStyle::IncludeIndependentTransformProperties);
       FloatPoint3D origin = transformOrigin(toLayoutBox(object));
-
-      unsigned renderingContextID = context.current.renderingContextID;
-      unsigned renderingContextIDForChildren = 0;
-      bool flattensInheritedTransform =
-          context.current.shouldFlattenInheritedTransform;
-      bool childrenFlattenInheritedTransform = true;
-
-      // TODO(trchen): transform-style should only be respected if a PaintLayer
-      // is created.
-      if (style.preserves3D()) {
-        // If a node with transform-style: preserve-3d does not exist in an
-        // existing rendering context, it establishes a new one.
-        if (!renderingContextID)
-          renderingContextID = PtrHash<const LayoutObject>::hash(&object);
-        renderingContextIDForChildren = renderingContextID;
-        childrenFlattenInheritedTransform = false;
-      }
-
       context.current.transform =
           object.getMutableForPainting()
               .ensurePaintProperties()
               .updateTransform(context.current.transform, matrix, origin,
                                flattensInheritedTransform, renderingContextID);
-      context.current.renderingContextID = renderingContextIDForChildren;
-      context.current.shouldFlattenInheritedTransform =
-          childrenFlattenInheritedTransform;
-      return;
+    }
+  } else {
+    if (!object.paintPropertiesValid()) {
+      if (auto* properties = object.getMutableForPainting().paintProperties())
+        properties->clearTransform();
     }
   }
-
-  if (auto* properties = object.getMutableForPainting().paintProperties())
-    properties->clearTransform();
 }
 
 void PaintPropertyTreeBuilder::updateEffect(
     const LayoutObject& object,
     PaintPropertyTreeBuilderContext& context) {
-  if (!object.styleRef().hasOpacity()) {
-    if (auto* properties = object.getMutableForPainting().paintProperties())
-      properties->clearEffect();
-    return;
+  if (object.paintPropertiesValid()) {
+    // No invalidation so update the context using existing properties.
+    if (object.paintProperties() && object.paintProperties()->effect())
+      context.currentEffect = object.paintProperties()->effect();
+  } else {
+    if (object.styleRef().hasOpacity()) {
+      context.currentEffect =
+          object.getMutableForPainting().ensurePaintProperties().updateEffect(
+              context.currentEffect, object.styleRef().opacity());
+    } else {
+      if (auto* properties = object.getMutableForPainting().paintProperties())
+        properties->clearEffect();
+    }
   }
-
-  context.currentEffect =
-      object.getMutableForPainting().ensurePaintProperties().updateEffect(
-          context.currentEffect, object.styleRef().opacity());
 }
 
 void PaintPropertyTreeBuilder::updateCssClip(
     const LayoutObject& object,
     PaintPropertyTreeBuilderContext& context) {
-  if (object.hasClip()) {
-    // Create clip node for descendants that are not fixed position.
-    // We don't have to setup context.absolutePosition.clip here because this
-    // object must be a container for absolute position descendants, and will
-    // copy from in-flow context later at updateOutOfFlowContext() step.
-    DCHECK(object.canContainAbsolutePositionObjects());
-    LayoutRect clipRect =
-        toLayoutBox(object).clipRect(context.current.paintOffset);
-    context.current.clip =
-        object.getMutableForPainting().ensurePaintProperties().updateCssClip(
-            context.current.clip, context.current.transform,
-            FloatRoundedRect(FloatRect(clipRect)));
-    return;
+  if (object.paintPropertiesValid()) {
+    // No invalidation so update the context using existing properties.
+    if (object.paintProperties() && object.paintProperties()->cssClip())
+      context.current.clip = object.paintProperties()->cssClip();
+  } else {
+    if (object.hasClip()) {
+      // Create clip node for descendants that are not fixed position.
+      // We don't have to setup context.absolutePosition.clip here because this
+      // object must be a container for absolute position descendants, and will
+      // copy from in-flow context later at updateOutOfFlowContext() step.
+      DCHECK(object.canContainAbsolutePositionObjects());
+      LayoutRect clipRect =
+          toLayoutBox(object).clipRect(context.current.paintOffset);
+      context.current.clip =
+          object.getMutableForPainting().ensurePaintProperties().updateCssClip(
+              context.current.clip, context.current.transform,
+              FloatRoundedRect(FloatRect(clipRect)));
+    } else {
+      if (auto* properties = object.getMutableForPainting().paintProperties())
+        properties->clearCssClip();
+    }
   }
-
-  if (auto* properties = object.getMutableForPainting().paintProperties())
-    properties->clearCssClip();
 }
 
 void PaintPropertyTreeBuilder::updateLocalBorderBoxContext(
     const LayoutObject& object,
     PaintPropertyTreeBuilderContext& context) {
+  if (object.paintPropertiesValid())
+    return;
+
   // Avoid adding an ObjectPaintProperties for non-boxes to save memory, since
   // we don't need them at the moment.
-  if (!object.isBox() && !object.hasLayer())
+  if (!object.isBox() && !object.hasLayer()) {
+    if (auto* properties = object.getMutableForPainting().paintProperties())
+      properties->clearLocalBorderBoxProperties();

[chrishtr, 2016/10/21 22:03:09]

Why is this change needed but wasn't in the old code?

[pdr., 2016/10/26 03:10:48]

This is just a cleanup so we don't leave unnecessary localBorderBoxProperties
objects when a object loses a layer.

     return;
+  }
 
   std::unique_ptr<ObjectPaintProperties::PropertyTreeStateWithOffset>
       borderBoxContext =
           wrapUnique(new ObjectPaintProperties::PropertyTreeStateWithOffset(
               context.current.paintOffset,
               PropertyTreeState(context.current.transform, context.current.clip,
                                 context.currentEffect,
                                 context.current.scroll)));
   object.getMutableForPainting()
       .ensurePaintProperties()
       .setLocalBorderBoxProperties(std::move(borderBoxContext));
 }
 
 // TODO(trchen): Remove this once we bake the paint offset into frameRect.
 void PaintPropertyTreeBuilder::updateScrollbarPaintOffset(
     const LayoutObject& object,
     const PaintPropertyTreeBuilderContext& context) {
+  if (object.paintPropertiesValid())
+    return;
+
   IntPoint roundedPaintOffset = roundedIntPoint(context.current.paintOffset);
   if (roundedPaintOffset != IntPoint() && object.isBoxModelObject()) {
     if (PaintLayerScrollableArea* scrollableArea =
             toLayoutBoxModelObject(object).getScrollableArea()) {
       if (scrollableArea->horizontalScrollbar() ||
           scrollableArea->verticalScrollbar()) {
         auto paintOffset = TransformationMatrix().translate(
             roundedPaintOffset.x(), roundedPaintOffset.y());
         object.getMutableForPainting()
             .ensurePaintProperties()
             .updateScrollbarPaintOffset(context.current.transform, paintOffset,
                                         FloatPoint3D());
         return;
       }
     }
   }
 
   if (auto* properties = object.getMutableForPainting().paintProperties())
     properties->clearScrollbarPaintOffset();
 }
 
 void PaintPropertyTreeBuilder::updateMainThreadScrollingReasons(
     const LayoutObject& object,
     PaintPropertyTreeBuilderContext& context) {
+  // TODO(pdr): Add property under-invalidation checking for main thread scroll
+  // reasons and ensure reason changes invalidate property trees.
   if (context.current.scroll &&
-      !object.document().settings()->threadedScrollingEnabled())
+      !object.document().settings()->threadedScrollingEnabled()) {
     context.current.scroll->addMainThreadScrollingReasons(
         MainThreadScrollingReason::kThreadedScrollingDisabled);
+  }
 
   if (object.isBackgroundAttachmentFixedObject()) {
     auto* scrollNode = context.current.scroll;
     while (
         scrollNode &&
         !scrollNode->hasMainThreadScrollingReasons(
             MainThreadScrollingReason::kHasBackgroundAttachmentFixedObjects)) {
       scrollNode->addMainThreadScrollingReasons(
           MainThreadScrollingReason::kHasBackgroundAttachmentFixedObjects);
       scrollNode = scrollNode->parent();
     }
   }
 }
 
 void PaintPropertyTreeBuilder::updateOverflowClip(
     const LayoutObject& object,
     PaintPropertyTreeBuilderContext& context) {
   if (!object.isBox())
     return;
   const LayoutBox& box = toLayoutBox(object);
 
+  if (object.paintPropertiesValid()) {
+    // No invalidation so update the context using existing properties.
+    const auto* properties = object.paintProperties();
+    if (properties && properties->overflowClip())
+      context.current.clip = properties->overflowClip();
+    return;
+  }
+
   // The <input> elements can't have contents thus CSS overflow property doesn't
   // apply.  However for layout purposes we do generate child layout objects for
   // them, e.g. button label.  We should clip the overflow from those children.
   // This is called control clip and we technically treat them like overflow
   // clip.
   LayoutRect clipRect;
   if (box.hasControlClip()) {
     clipRect = box.controlClipRect(context.current.paintOffset);
   } else if (box.hasOverflowClip() || box.styleRef().containsPaint() ||
              (box.isSVGRoot() &&
@@ skipping 32 matching lines @@
   return FloatPoint(
       floatValueForLength(style.perspectiveOriginX(), borderBoxSize.width()),
       floatValueForLength(style.perspectiveOriginY(), borderBoxSize.height()));
 }
 
 void PaintPropertyTreeBuilder::updatePerspective(
     const LayoutObject& object,
     PaintPropertyTreeBuilderContext& context) {
   const ComputedStyle& style = object.styleRef();
   if (!object.isBox() || !style.hasPerspective()) {
-    if (auto* properties = object.getMutableForPainting().paintProperties())
-      properties->clearPerspective();
+    if (!object.paintPropertiesValid()) {
+      if (auto* properties = object.getMutableForPainting().paintProperties())
+        properties->clearPerspective();
+    }
     return;
   }
 
-  // The perspective node must not flatten (else nothing will get
-  // perspective), but it should still extend the rendering context as most
-  // transform nodes do.
-  TransformationMatrix matrix =
-      TransformationMatrix().applyPerspective(style.perspective());
-  FloatPoint3D origin = perspectiveOrigin(toLayoutBox(object)) +
-                        toLayoutSize(context.current.paintOffset);
-  context.current.transform =
-      object.getMutableForPainting().ensurePaintProperties().updatePerspective(
-          context.current.transform, matrix, origin,
-          context.current.shouldFlattenInheritedTransform,
-          context.current.renderingContextID);
+  if (object.paintPropertiesValid()) {
+    // No invalidation so update the context using existing properties.
+    if (object.paintProperties() && object.paintProperties()->perspective())
+      context.current.transform = object.paintProperties()->perspective();
+  } else {
+    // The perspective node must not flatten (else nothing will get
+    // perspective), but it should still extend the rendering context as most
+    // transform nodes do.
+    TransformationMatrix matrix =
+        TransformationMatrix().applyPerspective(style.perspective());
+    FloatPoint3D origin = perspectiveOrigin(toLayoutBox(object)) +
+                          toLayoutSize(context.current.paintOffset);
+    context.current.transform =
+        object.getMutableForPainting()
+            .ensurePaintProperties()
+            .updatePerspective(context.current.transform, matrix, origin,
+                               context.current.shouldFlattenInheritedTransform,
+                               context.current.renderingContextID);
+  }
   context.current.shouldFlattenInheritedTransform = false;
 }
 
 void PaintPropertyTreeBuilder::updateSvgLocalToBorderBoxTransform(
     const LayoutObject& object,
     PaintPropertyTreeBuilderContext& context) {
   if (!object.isSVGRoot())
     return;
 
-  AffineTransform transformToBorderBox =
-      SVGRootPainter(toLayoutSVGRoot(object))
-          .transformToPixelSnappedBorderBox(context.current.paintOffset);
+  if (object.paintPropertiesValid()) {
+    // No invalidation so update the context using existing properties.
+    const auto* properties = object.paintProperties();
+    if (properties && properties->svgLocalToBorderBoxTransform()) {
+      context.current.transform = properties->svgLocalToBorderBoxTransform();
+      context.current.shouldFlattenInheritedTransform = false;
+      context.current.renderingContextID = 0;
+    }
+  } else {
+    AffineTransform transformToBorderBox =
+        SVGRootPainter(toLayoutSVGRoot(object))
+            .transformToPixelSnappedBorderBox(context.current.paintOffset);
+
+    if (transformToBorderBox.isIdentity()) {
+      if (auto* properties = object.getMutableForPainting().paintProperties())
+        properties->clearSvgLocalToBorderBoxTransform();
+    } else {
+      context.current.transform = object.getMutableForPainting()
+                                      .ensurePaintProperties()
+                                      .updateSvgLocalToBorderBoxTransform(
+                                          context.current.transform,
+                                          transformToBorderBox, FloatPoint3D());
+      context.current.shouldFlattenInheritedTransform = false;
+      context.current.renderingContextID = 0;
+    }
+  }
 
   // The paint offset is included in |transformToBorderBox| so SVG does not need
   // to handle paint offset internally.
   context.current.paintOffset = LayoutPoint();
-
-  if (transformToBorderBox.isIdentity()) {
-    if (auto* properties = object.getMutableForPainting().paintProperties())
-      properties->clearSvgLocalToBorderBoxTransform();
-    return;
-  }
-
-  context.current.transform =
-      object.getMutableForPainting()
-          .ensurePaintProperties()
-          .updateSvgLocalToBorderBoxTransform(
-              context.current.transform, transformToBorderBox, FloatPoint3D());
-  context.current.shouldFlattenInheritedTransform = false;
-  context.current.renderingContextID = 0;
 }
 
 void PaintPropertyTreeBuilder::updateScrollAndScrollTranslation(
     const LayoutObject& object,
     PaintPropertyTreeBuilderContext& context) {
+  if (object.paintPropertiesValid()) {
+    // No invalidation so update the context using existing properties.
+    if (object.paintProperties() && object.paintProperties()->scroll()) {
+      context.current.transform = object.paintProperties()->transform();
+      const auto* scroll = object.paintProperties()->scroll();
+      // TODO(pdr): Remove this const cast.
+      context.current.scroll = const_cast<ScrollPaintPropertyNode*>(scroll);
+      context.current.shouldFlattenInheritedTransform = false;
+    }
+    return;
+  }
+
   if (object.hasOverflowClip()) {
     const LayoutBox& box = toLayoutBox(object);
     const PaintLayerScrollableArea* scrollableArea = box.getScrollableArea();
     IntSize scrollOffset = box.scrolledContentOffset();
     if (!scrollOffset.isZero() || scrollableArea->scrollsOverflow()) {
       TransformationMatrix matrix = TransformationMatrix().translate(
           -scrollOffset.width(), -scrollOffset.height());
       context.current.transform =
           object.getMutableForPainting()
               .ensurePaintProperties()
@@ skipping 53 matching lines @@
     // absolute position container. However for fixed-position descendants we
     // need to insert the clip here if we are not a containing block ancestor of
     // them.
     auto* cssClip = object.getMutableForPainting().paintProperties()->cssClip();
 
     // Before we actually create anything, check whether in-flow context and
     // fixed-position context has exactly the same clip. Reuse if possible.
     if (context.fixedPosition.clip == cssClip->parent()) {
       context.fixedPosition.clip = cssClip;
     } else {
-      context.fixedPosition.clip =
-          object.getMutableForPainting()
-              .ensurePaintProperties()
-              .updateCssClipFixedPosition(
-                  context.fixedPosition.clip,
-                  const_cast<TransformPaintPropertyNode*>(
-                      cssClip->localTransformSpace()),
-                  cssClip->clipRect());
+      if (object.paintPropertiesValid()) {
+        // No invalidation so update the context using existing properties.
+        const auto* properties = object.paintProperties();
+        if (properties && properties->cssClipFixedPosition())
+          context.fixedPosition.clip = properties->cssClipFixedPosition();
+      } else {
+        context.fixedPosition.clip =
+            object.getMutableForPainting()
+                .ensurePaintProperties()
+                .updateCssClipFixedPosition(
+                    context.fixedPosition.clip,
+                    const_cast<TransformPaintPropertyNode*>(
+                        cssClip->localTransformSpace()),
+                    cssClip->clipRect());
+      }
       return;
     }
   }
 
-  if (auto* properties = object.getMutableForPainting().paintProperties())
-    properties->clearCssClipFixedPosition();
+  if (!object.paintPropertiesValid()) {
+    if (auto* properties = object.getMutableForPainting().paintProperties())
+      properties->clearCssClipFixedPosition();
+  }
 }
 
 // Override ContainingBlockContext based on the properties of a containing block
 // that was previously walked in a subtree other than the current subtree being
 // walked. Used for out-of-flow positioned descendants of multi-column spanner
 // when the containing block is not in the normal tree walk order.
 // For example:
 // <div id="columns" style="columns: 2">
 //   <div id="relative" style="position: relative">
 //     <div id="spanner" style="column-span: all">
@@ skipping 104 matching lines @@
     // Similar adjustment is done in LayoutTableCell::offsetFromContainer().
     if (boxModelObject.isTableCell()) {
       LayoutObject* parentRow = boxModelObject.parent();
       ASSERT(parentRow && parentRow->isTableRow());
       context.current.paintOffset.moveBy(
           -toLayoutBox(parentRow)->topLeftLocation());
     }
   }
 }
 
-void PaintPropertyTreeBuilder::buildTreeNodesForSelf(
+void PaintPropertyTreeBuilder::updatePropertiesForSelf(
     const LayoutObject& object,
     PaintPropertyTreeBuilderContext& context) {
   if (!object.isBoxModelObject() && !object.isSVG())
     return;
 
+#ifndef NDEBUG
+  auto underInvalidationChecker =
+      ObjectUnderInvalidationCheckScope::createIfNeeded(object);
+#endif
+
   deriveBorderBoxFromContainerContext(object, context);
 
   updatePaintOffsetTranslation(object, context);
   updateTransform(object, context);
   updateEffect(object, context);
   updateCssClip(object, context);
   updateLocalBorderBoxContext(object, context);
   updateScrollbarPaintOffset(object, context);
   updateMainThreadScrollingReasons(object, context);
 }
 
-void PaintPropertyTreeBuilder::buildTreeNodesForChildren(
+void PaintPropertyTreeBuilder::updatePropertiesForChildren(
     const LayoutObject& object,
     PaintPropertyTreeBuilderContext& context) {
   if (!object.isBoxModelObject() && !object.isSVG())
     return;
 
+#ifndef NDEBUG
+  auto underInvalidationChecker =
+      ObjectUnderInvalidationCheckScope::createIfNeeded(object);
+#endif
+
   updateOverflowClip(object, context);
   updatePerspective(object, context);
   updateSvgLocalToBorderBoxTransform(object, context);
   updateScrollAndScrollTranslation(object, context);
   updateOutOfFlowContext(object, context);
 }
 
 }  // namespace blink