Optimize scroll adjustment for paint invalidation

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

Index: third_party/WebKit/Source/core/paint/PaintInvalidator.h
diff --git a/third_party/WebKit/Source/core/paint/PaintInvalidator.h b/third_party/WebKit/Source/core/paint/PaintInvalidator.h
index 6bdf380497104a3af96d4c1df14edcd4b6e71f06..d1871ca15b5653cea49edff06adc8e89f71115e3 100644
--- a/third_party/WebKit/Source/core/paint/PaintInvalidator.h
+++ b/third_party/WebKit/Source/core/paint/PaintInvalidator.h
@@ -30,6 +30,7 @@ struct PaintInvalidatorContext {
         forcedSubtreeInvalidationFlags(
             parentContext.forcedSubtreeInvalidationFlags),
         paintInvalidationContainer(parentContext.paintInvalidationContainer),
+        scrollAdjustment(parentContext.scrollAdjustment),
         paintInvalidationContainerForStackedContents(
             parentContext.paintInvalidationContainerForStackedContents),
         paintingLayer(parentContext.paintingLayer) {}
@@ -61,6 +62,11 @@ struct PaintInvalidatorContext {
   // It is the enclosing composited object.
   const LayoutBoxModelObject* paintInvalidationContainer = nullptr;
 
+  // Adjusts scrolling contents coordinates in non-composited paint invalidation
+  // container into container coordinates. It's empty for non-scrolling or
+  // composited-scrolling paint invalidation container.
+  IntSize scrollAdjustment;
+
   // The current paint invalidation container for stacked contents (stacking
   // contexts or positioned objects).  It is the nearest ancestor composited
   // object which establishes a stacking context.  See