Add background attachment fixed main thread scrolling reason [spv2]

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

Index: third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.h
diff --git a/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.h b/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.h
index fc15eb58e337397da22220ce51e3c38ad2218dd2..a036b0fd9b483f3c425062e16b07a4a6ad8ae462 100644
--- a/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.h
+++ b/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.h
@@ -47,7 +47,7 @@ struct PaintPropertyTreeBuilderContext {
         // The scroll node contains information for scrolling such as the parent scroll space, the
         // extent that can be scrolled, etc. Because scroll nodes reference a scroll offset
         // transform, scroll nodes should be updated if the transform tree changes.
-        const ScrollPaintPropertyNode* scroll = nullptr;
+        ScrollPaintPropertyNode* scroll = nullptr;
     };
 
     ContainingBlockContext current;
@@ -88,6 +88,7 @@ private:
     static void updateCssClip(const LayoutObject&, PaintPropertyTreeBuilderContext&);
     static void updateLocalBorderBoxContext(const LayoutObject&, PaintPropertyTreeBuilderContext&);
     static void updateScrollbarPaintOffset(const LayoutObject&, const PaintPropertyTreeBuilderContext&);
+    static void updateMainThreadScrollingReasons(const LayoutObject&, PaintPropertyTreeBuilderContext&);
     static void updateOverflowClip(const LayoutObject&, PaintPropertyTreeBuilderContext&);
     static void updatePerspective(const LayoutObject&, PaintPropertyTreeBuilderContext&);
     static void updateSvgLocalToBorderBoxTransform(const LayoutObject&, PaintPropertyTreeBuilderContext&);