Simply rules for compositing fixed position elements

Source/core/page/scrolling/ScrollingCoordinator.cpp

Index: Source/core/page/scrolling/ScrollingCoordinator.cpp
diff --git a/Source/core/page/scrolling/ScrollingCoordinator.cpp b/Source/core/page/scrolling/ScrollingCoordinator.cpp
index 44ca7986fe900422bdbcd190354f20b8ab35d3df..0fd7da969ccb968afaf5a424a41b9e8d8db8f6aa 100644
--- a/Source/core/page/scrolling/ScrollingCoordinator.cpp
+++ b/Source/core/page/scrolling/ScrollingCoordinator.cpp
@@ -889,10 +889,6 @@ bool ScrollingCoordinator::hasVisibleSlowRepaintViewportConstrainedObjects(Frame
         if (!viewportConstrainedObject->isBoxModelObject() || !viewportConstrainedObject->hasLayer())
             return true;
         RenderLayer* layer = toRenderBoxModelObject(viewportConstrainedObject)->layer();
-        // Any explicit reason that a fixed position element is not composited shouldn't cause slow scrolling.
-        if (layer->compositingState() != PaintsIntoOwnBacking && layer->viewportConstrainedNotCompositedReason() == RenderLayer::NoNotCompositedReason)
-            return true;
-
         // Composited layers that actually paint into their enclosing ancestor
         // must also force main thread scrolling.
         if (layer->compositingState() == HasOwnBackingButPaintsIntoAncestor)