[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 50a63a3e6fb39273db67ebc6f3932bc0193f7759..a6b3dcc52da8f3f2cfa375cab0cd8bb3bbb19025 100644
--- a/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp
+++ b/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp
@@ -2199,6 +2199,37 @@ void CompositedLayerMapping::UpdateShouldFlattenTransform() {
   }
 }
 
+struct AnimatingData {
+  STACK_ALLOCATED()
+  Persistent<Node> owning_node = nullptr;
+  Persistent<Element> animating_element = nullptr;
+  const ComputedStyle* animating_style = nullptr;
+};
+
+void GetAnimatingData(PaintLayer& paint_layer, AnimatingData& data) {
+  if (!RuntimeEnabledFeatures::compositorWorkerEnabled())
+    return;
+
+  data.owning_node = paint_layer.GetLayoutObject().GetNode();
+
+  if (!data.owning_node)
+    return;
+
+  Document& document = data.owning_node->GetDocument();
+  Element* scrolling_element = document.ScrollingElementNoLayout();
+  if (data.owning_node->IsElementNode() &&
+      (!RuntimeEnabledFeatures::rootLayerScrollingEnabled() ||
+       data.owning_node != scrolling_element)) {
+    data.animating_element = ToElement(data.owning_node);
+    data.animating_style = paint_layer.GetLayoutObject().Style();
+  } else if (data.owning_node->IsDocumentNode() &&
+             RuntimeEnabledFeatures::rootLayerScrollingEnabled()) {
+    data.owning_node = data.animating_element = scrolling_element;
+    if (scrolling_element && scrolling_element->GetLayoutObject())
+      data.animating_style = scrolling_element->GetLayoutObject()->Style();
+  }
+}
+
 // Some background on when you receive an element id or mutable properties.
 //
 // element id:
@@ -2213,52 +2244,34 @@ 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;
 
-  Node* owning_node = owning_layer_.GetLayoutObject().GetNode();
-  Element* animating_element = nullptr;
-  const ComputedStyle* animating_style = nullptr;
-  if (owning_node) {
-    Document& document = owning_node->GetDocument();
-    Element* scrolling_element = document.ScrollingElementNoLayout();
-    if (owning_node->IsElementNode() &&
-        (!RuntimeEnabledFeatures::rootLayerScrollingEnabled() ||
-         owning_node != scrolling_element)) {
-      animating_element = ToElement(owning_node);
-      animating_style = owning_layer_.GetLayoutObject().Style();
-    } else if (owning_node->IsDocumentNode() &&
-               RuntimeEnabledFeatures::rootLayerScrollingEnabled()) {
-      owning_node = animating_element = scrolling_element;
-      if (scrolling_element && scrolling_element->GetLayoutObject())
-        animating_style = scrolling_element->GetLayoutObject()->Style();
-    }
-  }
+  AnimatingData data;
+  GetAnimatingData(owning_layer_, data);
+
+  CompositorElementId element_id;
+  if (data.animating_style && data.animating_style->HasCompositorProxy()) {
+    // Compositor proxy element ids cannot be based on PaintLayers, since
+    // those are not kept alive by script across frames.
+    element_id = CompositorElementIdFromDOMNodeId(
+        DOMNodeIds::IdForNode(data.owning_node),
+        CompositorElementIdNamespace::kPrimaryCompositorProxy);
 
-  if (RuntimeEnabledFeatures::compositorWorkerEnabled() && animating_style &&
-      animating_style->HasCompositorProxy()) {
     uint32_t compositor_mutable_properties =
-        animating_element->CompositorMutableProperties();
-    element_id = DOMNodeIds::IdForNode(owning_node);
+        data.animating_element->CompositorMutableProperties();
     primary_mutable_properties = (CompositorMutableProperty::kOpacity |
                                   CompositorMutableProperty::kTransform) &
                                  compositor_mutable_properties;
     scroll_mutable_properties = (CompositorMutableProperty::kScrollLeft |
                                  CompositorMutableProperty::kScrollTop) &
                                 compositor_mutable_properties;
+  } else {
+    element_id = CompositorElementIdFromPaintLayerId(
+        owning_layer_.UniqueId(), CompositorElementIdNamespace::kPrimary);
   }
 
-  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);
-  }
-
-  graphics_layer_->SetElementId(compositor_element_id);
+  graphics_layer_->SetElementId(element_id);
   graphics_layer_->SetCompositorMutableProperties(primary_mutable_properties);
 
   // We always set the elementId for m_scrollingContentsLayer since it can be
@@ -2380,13 +2393,21 @@ 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));
+      AnimatingData data;
+      GetAnimatingData(owning_layer_, data);
+
+      CompositorElementId element_id;
+      if (data.animating_style && data.animating_style->HasCompositorProxy()) {
+        element_id = CompositorElementIdFromDOMNodeId(
+            DOMNodeIds::IdForNode(data.owning_node),
+            CompositorElementIdNamespace::kScrollCompositorProxy);
+      } else {
+        element_id = CompositorElementIdFromPaintLayerId(
+            owning_layer_.UniqueId(), CompositorElementIdNamespace::kScroll);
       }
 
+      scrolling_contents_layer_->SetElementId(element_id);
+
       scrolling_layer_->AddChild(scrolling_contents_layer_.get());
 
       layer_changed = true;