Optimize scroll adjustment for paint invalidation

third_party/WebKit/Source/core/layout/PaintInvalidationState.cpp

Index: third_party/WebKit/Source/core/layout/PaintInvalidationState.cpp
diff --git a/third_party/WebKit/Source/core/layout/PaintInvalidationState.cpp b/third_party/WebKit/Source/core/layout/PaintInvalidationState.cpp
index 086b5b51fe0577a335892660e0d1b486135072ab..db7c066603e031565dbc37c3a0b61422074c27e6 100644
--- a/third_party/WebKit/Source/core/layout/PaintInvalidationState.cpp
+++ b/third_party/WebKit/Source/core/layout/PaintInvalidationState.cpp
@@ -43,6 +43,8 @@ PaintInvalidationState::PaintInvalidationState(
       m_cachedOffsetsEnabled(true),
       m_cachedOffsetsForAbsolutePositionEnabled(true),
       m_paintInvalidationContainer(&layoutView.containerForPaintInvalidation()),
+      m_scrollAdjustment(
+          m_paintInvalidationContainer->scrollAdjustmentForPaintInvalidation()),
       m_paintInvalidationContainerForStackedContents(
           m_paintInvalidationContainer),
       m_containerForAbsolutePosition(layoutView),
@@ -85,6 +87,7 @@ PaintInvalidationState::PaintInvalidationState(
       m_cachedOffsetsForAbsolutePositionEnabled(
           parentState.m_cachedOffsetsForAbsolutePositionEnabled),
       m_paintInvalidationContainer(parentState.m_paintInvalidationContainer),
+      m_scrollAdjustment(parentState.m_scrollAdjustment),
       m_paintInvalidationContainerForStackedContents(
           parentState.m_paintInvalidationContainerForStackedContents),
       m_containerForAbsolutePosition(
@@ -120,6 +123,7 @@ PaintInvalidationState::PaintInvalidationState(
   DCHECK(parentState.m_didUpdateForChildren);
 #endif
 
+  const auto* oldPaintInvalidationContainer = m_paintInvalidationContainer;
   if (currentObject.isPaintInvalidationContainer()) {
     m_paintInvalidationContainer = toLayoutBoxModelObject(&currentObject);
     if (currentObject.styleRef().isStackingContext())
@@ -167,6 +171,15 @@ PaintInvalidationState::PaintInvalidationState(
           PaintInvalidatorContext::ForcedSubtreeFullInvalidation;
   }
 
+  if (m_paintInvalidationContainer != oldPaintInvalidationContainer) {
+    m_scrollAdjustment =
+        m_paintInvalidationContainer->scrollAdjustmentForPaintInvalidation();
+  } else {
+    DCHECK(
+        m_scrollAdjustment ==
+        m_paintInvalidationContainer->scrollAdjustmentForPaintInvalidation());
+  }
+
   if (!currentObject.isBoxModelObject() && !currentObject.isSVG())
     return;
 
@@ -442,14 +455,13 @@ LayoutPoint PaintInvalidationState::computeLocationInBacking(
       point = slowLocalToAncestorPoint(
           m_currentObject, *m_paintInvalidationContainer, FloatPoint());
     }
+
+    point.move(m_scrollAdjustment);
   }
 
   PaintLayer::mapPointInPaintInvalidationContainerToBacking(
       *m_paintInvalidationContainer, point);
 
-  point.move(m_currentObject.scrollAdjustmentForPaintInvalidation(
-      *m_paintInvalidationContainer));
-
   return LayoutPoint(point);
 }
 
@@ -493,8 +505,8 @@ LayoutRect PaintInvalidationState::computeVisualRectInBackingForSVG() const {
 
   m_currentObject.adjustVisualRectForRasterEffects(rect);
 
-  rect.move(m_currentObject.scrollAdjustmentForPaintInvalidation(
-      *m_paintInvalidationContainer));
+  if (m_currentObject != m_paintInvalidationContainer)
+    rect.move(m_scrollAdjustment);
 
   return rect;
 }
@@ -551,8 +563,8 @@ void PaintInvalidationState::mapLocalRectToVisualRectInBacking(
 
   m_currentObject.adjustVisualRectForRasterEffects(rect);
 
-  rect.move(m_currentObject.scrollAdjustmentForPaintInvalidation(
-      *m_paintInvalidationContainer));
+  if (m_currentObject != m_paintInvalidationContainer)
+    rect.move(m_scrollAdjustment);
 }
 
 void PaintInvalidationState::addClipRectRelativeToPaintOffset(