Revert of Replace RenderFullScreen with top layer

Source/core/dom/Element.cpp

Index: Source/core/dom/Element.cpp
diff --git a/Source/core/dom/Element.cpp b/Source/core/dom/Element.cpp
index c528b8b77d020664125a92a4a8982195bb92fcdb..ebdb3a0f525af79c9bf072abcb6fb6a00dca48d5 100644
--- a/Source/core/dom/Element.cpp
+++ b/Source/core/dom/Element.cpp
@@ -2796,8 +2796,7 @@ bool Element::needsPseudoElement(PseudoId pseudoId, const RenderStyle& style) co
         return false;
     if (!renderer() || !pseudoElementRendererIsNeeded(&style))
         return false;
-    /* It's safe to have a backdrop since its renderer is always a child of RenderView. */
-    if (pseudoId != BACKDROP && !renderer()->canHaveGeneratedChildren())
+    if (!renderer()->canHaveGeneratedChildren())
         return false;
     return true;
 }