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

third_party/WebKit/Source/core/animation/CompositorAnimations.cpp

Index: third_party/WebKit/Source/core/animation/CompositorAnimations.cpp
diff --git a/third_party/WebKit/Source/core/animation/CompositorAnimations.cpp b/third_party/WebKit/Source/core/animation/CompositorAnimations.cpp
index 0179f6125b962d1e985b8e32604043ca309fc759..7b2c1ea26302936149a29143f88714e313985ff6 100644
--- a/third_party/WebKit/Source/core/animation/CompositorAnimations.cpp
+++ b/third_party/WebKit/Source/core/animation/CompositorAnimations.cpp
@@ -446,15 +446,16 @@ void CompositorAnimations::AttachCompositedLayers(Element& element,
     return;
 
   if (!element.GetLayoutObject() ||

[wkorman, 2017/05/18 00:45:58]

nit: consider local var for element.GetLayoutObject() to shorten refs

-      !element.GetLayoutObject()->IsBoxModelObject())
+      !element.GetLayoutObject()->IsBoxModelObject() ||
+      !element.GetLayoutObject()->HasLayer())
     return;
 
+  PaintLayer* layer =
+      ToLayoutBoxModelObject(element.GetLayoutObject())->Layer();
+
   // Composited animations do not depend on a composited layer mapping for SPv2.
   if (!RuntimeEnabledFeatures::slimmingPaintV2Enabled()) {
-    PaintLayer* layer =
-        ToLayoutBoxModelObject(element.GetLayoutObject())->Layer();
-
-    if (!layer || !layer->IsAllowedToQueryCompositingState() ||
+    if (!layer->IsAllowedToQueryCompositingState() ||
         !layer->GetCompositedLayerMapping() ||
         !layer->GetCompositedLayerMapping()->MainGraphicsLayer())
       return;
@@ -466,8 +467,8 @@ void CompositorAnimations::AttachCompositedLayers(Element& element,
   }
 
   CompositorAnimationPlayer* compositor_player = animation.CompositorPlayer();
-  compositor_player->AttachElement(CompositorElementIdFromDOMNodeId(
-      DOMNodeIds::IdForNode(&element), CompositorElementIdNamespace::kPrimary));
+  compositor_player->AttachElement(CompositorElementIdFromPaintLayerId(
+      layer->UniqueId(), CompositorElementIdNamespace::kPrimary));
 }
 
 bool CompositorAnimations::ConvertTimingForCompositor(