End-to-end prototype of compositor scrolling with slimming paint v2

third_party/WebKit/Source/core/frame/FrameView.cpp

Index: third_party/WebKit/Source/core/frame/FrameView.cpp
diff --git a/third_party/WebKit/Source/core/frame/FrameView.cpp b/third_party/WebKit/Source/core/frame/FrameView.cpp
index 9aa2afd891f4c5db3153c129e59e86973d43ca32..19375038e80988b0a28bff8360441f2222f037ee 100644
--- a/third_party/WebKit/Source/core/frame/FrameView.cpp
+++ b/third_party/WebKit/Source/core/frame/FrameView.cpp
@@ -3158,11 +3158,33 @@ void FrameView::pushPaintArtifactToCompositor() {
 
   SCOPED_BLINK_UMA_HISTOGRAM_TIMER("Blink.Compositing.UpdateTime");
 
+  // TODO(pdr): This map should be cached.
+  PaintArtifactCompositor::ScrollClientMap scrollClientMap;
+  if (m_scrollableAreas) {
+    for (auto scrollableArea : *m_scrollableAreas) {
+      const auto* box = scrollableArea->layoutBox();
+      if (!box)
+        continue;
+      const auto* properties = box->paintProperties();
+      if (!properties)
+        continue;
+      const auto* scrollTranslation = properties->scrollTranslation();
+      if (!scrollTranslation)
+        continue;
+      const auto* scrollNode = scrollTranslation->scrollNode();
+      scrollClientMap.set(scrollNode, scrollableArea.get());
+    }
+  }
+  if (const auto* scrollTranslationNode = scrollTranslation()) {
+    if (auto* scrollableArea = getScrollableArea())
+      scrollClientMap.set(scrollTranslationNode->scrollNode(), scrollableArea);
+  }
+
   DCHECK(m_geometryMapper.get());
   m_paintArtifactCompositor->update(
       m_paintController->paintArtifact(),
       m_paintController->paintChunksRasterInvalidationTrackingMap(),
-      m_isStoringCompositedLayerDebugInfo, *m_geometryMapper);
+      m_isStoringCompositedLayerDebugInfo, *m_geometryMapper, scrollClientMap);
 }
 
 std::unique_ptr<JSONObject> FrameView::compositedLayersAsJSON(