Optimize scroll adjustment for paint invalidation

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

Index: third_party/WebKit/Source/core/paint/PaintInvalidator.cpp
diff --git a/third_party/WebKit/Source/core/paint/PaintInvalidator.cpp b/third_party/WebKit/Source/core/paint/PaintInvalidator.cpp
index 1c06307669e9806504882409f305d5f9f4682975..d7c7721813fabaa2e3b1e56015c14657a4ba085e 100644
--- a/third_party/WebKit/Source/core/paint/PaintInvalidator.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintInvalidator.cpp
@@ -137,6 +137,7 @@ static LayoutRect mapLocalRectToVisualRectInBacking(
 
     // Convert the result to the container's contents space.
     result.moveBy(-context.paintInvalidationContainer->paintOffset());
+    result.move(context.scrollAdjustment);
   }
 
   object.adjustVisualRectForRasterEffects(result);
@@ -144,9 +145,6 @@ static LayoutRect mapLocalRectToVisualRectInBacking(
   PaintLayer::mapRectInPaintInvalidationContainerToBacking(
       *context.paintInvalidationContainer, result);
 
-  result.move(object.scrollAdjustmentForPaintInvalidation(
-      *context.paintInvalidationContainer));
-
   return result;
 }
 
@@ -195,6 +193,7 @@ LayoutPoint PaintInvalidator::computeLocationInBacking(
 
     // Convert the result to the container's contents space.
     point.moveBy(-context.paintInvalidationContainer->paintOffset());
+    point.move(context.scrollAdjustment);
   }
 
   if (context.paintInvalidationContainer->layer()->groupedMapping()) {
@@ -204,9 +203,6 @@ LayoutPoint PaintInvalidator::computeLocationInBacking(
     point = LayoutPoint(floatPoint);
   }
 
-  point.move(object.scrollAdjustmentForPaintInvalidation(
-      *context.paintInvalidationContainer));
-
   return point;
 }
 
@@ -290,6 +286,8 @@ class ScopedUndoFrameViewContentClipAndScroll {
 void PaintInvalidator::updatePaintInvalidationContainer(
     const LayoutObject& object,
     PaintInvalidatorContext& context) {
+  const auto* oldPaintInvalidationContainer =
+      context.paintInvalidationContainer;
   if (object.isPaintInvalidationContainer()) {
     context.paintInvalidationContainer = toLayoutBoxModelObject(&object);
     if (object.styleRef().isStackingContext())
@@ -343,6 +341,15 @@ void PaintInvalidator::updatePaintInvalidationContainer(
     }
   }
 
+  if (context.paintInvalidationContainer != oldPaintInvalidationContainer) {
+    context.scrollAdjustment = context.paintInvalidationContainer
+                                   ->scrollAdjustmentForPaintInvalidation();
+  } else {
+    DCHECK(context.scrollAdjustment ==
+           context.paintInvalidationContainer
+               ->scrollAdjustmentForPaintInvalidation());
+  }
+
   DCHECK(context.paintInvalidationContainer ==
          object.containerForPaintInvalidation());
   DCHECK(context.paintingLayer == object.paintingLayer());
@@ -399,6 +406,8 @@ void PaintInvalidator::invalidatePaintIfNeeded(
   context.paintInvalidationContainer =
       context.paintInvalidationContainerForStackedContents =
           &layoutView->containerForPaintInvalidation();
+  context.scrollAdjustment = context.paintInvalidationContainer
+                                 ->scrollAdjustmentForPaintInvalidation();
   context.paintingLayer = layoutView->layer();
 
   if (!RuntimeEnabledFeatures::rootLayerScrollingEnabled()) {