Add compositor element id for scroll nodes in SPv2.

third_party/WebKit/Source/platform/graphics/paint/ScrollPaintPropertyNode.cpp

Index: third_party/WebKit/Source/platform/graphics/paint/ScrollPaintPropertyNode.cpp
diff --git a/third_party/WebKit/Source/platform/graphics/paint/ScrollPaintPropertyNode.cpp b/third_party/WebKit/Source/platform/graphics/paint/ScrollPaintPropertyNode.cpp
index 89f043502c8cd4ad13bd6f279fb8148073f26551..09b623aadda84f0396c18166d68095290f7ae12e 100644
--- a/third_party/WebKit/Source/platform/graphics/paint/ScrollPaintPropertyNode.cpp
+++ b/third_party/WebKit/Source/platform/graphics/paint/ScrollPaintPropertyNode.cpp
@@ -25,12 +25,14 @@ String ScrollPaintPropertyNode::toString() const {
   return String::format(
       "parent=%p scrollOffsetTranslation=%s clip=%s bounds=%s "
       "userScrollableHorizontal=%s"
-      " userScrollableVertical=%s mainThreadScrollingReasons=%s",
+      " userScrollableVertical=%s mainThreadScrollingReasons=%s"
+      "compositorElementId=(%d, %d)",
       m_parent.get(), scrollOffset.toString().ascii().data(),
       m_clip.toString().ascii().data(), m_bounds.toString().ascii().data(),
       m_userScrollableHorizontal ? "yes" : "no",
       m_userScrollableVertical ? "yes" : "no",
-      mainThreadScrollingReasonsAsText.c_str());
+      mainThreadScrollingReasonsAsText.c_str(), m_compositorElementId.primaryId,
+      m_compositorElementId.secondaryId);
 }
 
 #if DCHECK_IS_ON()