Incrementally build main thread scrolling reasons [spv2]

third_party/WebKit/Source/core/layout/LayoutObject.h

Index: third_party/WebKit/Source/core/layout/LayoutObject.h
diff --git a/third_party/WebKit/Source/core/layout/LayoutObject.h b/third_party/WebKit/Source/core/layout/LayoutObject.h
index 0ba1003ccdd46c1af60c31ba6c1eb1abb933836d..1e94872db340e509d0aa852af59f2e22f1cd9e74 100644
--- a/third_party/WebKit/Source/core/layout/LayoutObject.h
+++ b/third_party/WebKit/Source/core/layout/LayoutObject.h
@@ -1728,6 +1728,13 @@ class CORE_EXPORT LayoutObject : public ImageResourceObserver,
   void setNeedsPaintPropertyUpdate() {
     m_bitfields.setNeedsPaintPropertyUpdate(true);
   }
+  // TODO(pdr): This can be removed once we have more granular update flags.
+  void setAllAncestorsNeedPaintPropertyUpdate() {
+    if (m_parent) {
+      m_parent->setNeedsPaintPropertyUpdate();
+      m_parent->setAllAncestorsNeedPaintPropertyUpdate();
+    }
+  }
   void clearNeedsPaintPropertyUpdate() {
     DCHECK_EQ(document().lifecycle().state(), DocumentLifecycle::InPrePaint);
     m_bitfields.setNeedsPaintPropertyUpdate(false);