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

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

 /*
  * Copyright (C) 2009, 2010 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 1181 matching lines @@
     if (ScrollingCoordinator* scrolling_coordinator =
             this->GetScrollingCoordinator())
       scrolling_coordinator->SetLayerIsContainerForFixedPositionLayers(
           scroll_layer_.get(), true);
 
     // In RLS mode, LayoutView scrolling contents layer gets this element ID (in
     // CompositedLayerMapping::updateElementIdAndCompositorMutableProperties).
     if (!RuntimeEnabledFeatures::rootLayerScrollingEnabled()) {
       scroll_layer_->SetElementId(CompositorElementIdFromDOMNodeId(
           DOMNodeIds::IdForNode(&layout_view_.GetDocument()),
-          CompositorElementIdNamespace::kScroll));
+          CompositorElementIdNamespace::kRootScroll));
     }
 
     // Hook them up
     overflow_controls_host_layer_->AddChild(container_layer_.get());
     container_layer_->AddChild(scroll_layer_.get());
     scroll_layer_->AddChild(root_content_layer_.get());
 
     FrameViewDidChangeSize();
   }
 
@@ skipping 160 matching lines @@
   } else if (graphics_layer == scroll_layer_.get()) {
     name = "Frame Scrolling Layer";
   } else {
     NOTREACHED();
   }
 
   return name;
 }
 
 }  // namespace blink