[SPv1] Always set a CompositorElementId on main graphics layers; use PaintLayer id.

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

Index: third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.cpp
diff --git a/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.cpp b/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.cpp
index e61d98d7d9afa174a98d946ae9132cedf2e53e79..13f21dc1ef2318e2d34684d85a9e6bd55ce5bf08 100644
--- a/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.cpp
@@ -72,12 +72,11 @@ static bool UpdateContentClip(
   return true;
 }
 
-static CompositorElementId CreateDomNodeBasedCompositorElementId(
+static CompositorElementId CreatePaintLayereBasedCompositorElementId(
     const LayoutObject& object) {
-  // TODO(wkorman): Centralize this implementation with similar across
-  // animation, scrolling and compositing logic.
-  return CompositorElementIdFromDOMNodeId(
-      DOMNodeIds::IdForNode(object.GetNode()),
+  DCHECK(object.IsBoxModelObject() && object.HasLayer());
+  return CompositorElementIdFromPaintLayerId(
+      ToLayoutBoxModelObject(object).Layer()->UniqueId(),
       CompositorElementIdNamespace::kPrimary);
 }
 
@@ -97,7 +96,7 @@ static bool UpdateScrollTranslation(
     WebLayerScrollClient* scroll_client) {
   DCHECK(!RuntimeEnabledFeatures::rootLayerScrollingEnabled());
   CompositorElementId compositor_element_id =
-      CreateDomNodeBasedCompositorElementId(*frame_view.GetLayoutView());
+      CreatePaintLayereBasedCompositorElementId(*frame_view.GetLayoutView());
   if (auto* existing_scroll_translation = frame_view.ScrollTranslation()) {
     auto existing_reasons = existing_scroll_translation->ScrollNode()
                                 ->GetMainThreadScrollingReasons();
@@ -1195,9 +1194,9 @@ void PaintPropertyTreeBuilder::UpdatePaintProperties(
   if (needs_paint_properties && !had_paint_properties) {
     ObjectPaintProperties& paint_properties =
         object.GetMutableForPainting().EnsurePaintProperties();
-    if (RuntimeEnabledFeatures::slimmingPaintV2Enabled()) {
+    if (RuntimeEnabledFeatures::slimmingPaintV2Enabled() && object.HasLayer()) {
       paint_properties.SetCompositorElementId(
-          CreateDomNodeBasedCompositorElementId(object));
+          CreatePaintLayereBasedCompositorElementId(object));
     }
   } else if (!needs_paint_properties && had_paint_properties) {
     object.GetMutableForPainting().ClearPaintProperties();