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

third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp

Index: third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp
diff --git a/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp b/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp
index 5fb632f3340bba1fa95377e07e6af8f1517f8c82..99f71edc64fdffa3d7b21c21efefb1525b23a9c4 100644
--- a/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp
+++ b/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp
@@ -2207,7 +2207,6 @@ void CompositedLayerMapping::UpdateShouldFlattenTransform() {
 // well as the mutable properties for all layers may change according to the
 // rules above so we update those values here.
 void CompositedLayerMapping::UpdateElementIdAndCompositorMutableProperties() {
-  int element_id = 0;
   uint32_t primary_mutable_properties = CompositorMutableProperty::kNone;
   uint32_t scroll_mutable_properties = CompositorMutableProperty::kNone;
 
@@ -2234,7 +2233,6 @@ void CompositedLayerMapping::UpdateElementIdAndCompositorMutableProperties() {
       animating_style->HasCompositorProxy()) {
     uint32_t compositor_mutable_properties =
         animating_element->CompositorMutableProperties();
-    element_id = DOMNodeIds::IdForNode(owning_node);
     primary_mutable_properties = (CompositorMutableProperty::kOpacity |
                                   CompositorMutableProperty::kTransform) &
                                  compositor_mutable_properties;
@@ -2243,14 +2241,9 @@ void CompositedLayerMapping::UpdateElementIdAndCompositorMutableProperties() {
                                 compositor_mutable_properties;
   }
 
-  if (animating_style && animating_style->ShouldCompositeForCurrentAnimations())
-    element_id = DOMNodeIds::IdForNode(owning_node);
-
-  CompositorElementId compositor_element_id;
-  if (element_id) {
-    compositor_element_id = CompositorElementIdFromDOMNodeId(
-        element_id, CompositorElementIdNamespace::kPrimary);
-  }
+  CompositorElementId compositor_element_id =
+      CompositorElementIdFromPaintLayerId(
+          owning_layer_.UniqueId(), CompositorElementIdNamespace::kPrimary);
 
   graphics_layer_->SetElementId(compositor_element_id);
   graphics_layer_->SetCompositorMutableProperties(primary_mutable_properties);
@@ -2374,12 +2367,9 @@ bool CompositedLayerMapping::UpdateScrollingLayers(
       scrolling_contents_layer_ =
           CreateGraphicsLayer(kCompositingReasonLayerForScrollingContents);
 
-      if (Node* owning_node = owning_layer_.GetLayoutObject().GetNode()) {
-        scrolling_contents_layer_->SetElementId(
-            CompositorElementIdFromDOMNodeId(
-                DOMNodeIds::IdForNode(owning_node),
-                CompositorElementIdNamespace::kScroll));
-      }
+      scrolling_contents_layer_->SetElementId(
+          CompositorElementIdFromPaintLayerId(
+              owning_layer_.UniqueId(), CompositorElementIdNamespace::kScroll));
 
       scrolling_layer_->AddChild(scrolling_contents_layer_.get());