Revert of Replace RenderFullScreen with top layer

Source/core/dom/Document.cpp

Index: Source/core/dom/Document.cpp
diff --git a/Source/core/dom/Document.cpp b/Source/core/dom/Document.cpp
index ff03ea5951396e3482729a727cd8ab5c37cdbb9a..e6f0a2152cfab98a07f826d7dee7798685d4885b 100644
--- a/Source/core/dom/Document.cpp
+++ b/Source/core/dom/Document.cpp
@@ -4775,15 +4775,9 @@ void Document::removeFromTopLayer(Element* element)
 
 HTMLDialogElement* Document::activeModalDialog() const
 {
-    Vector<RefPtr<Element> >::const_reverse_iterator end = m_topLayerElements.rend();
-    for (Vector<RefPtr<Element> >::const_reverse_iterator it = m_topLayerElements.rbegin(); it != end; ++it) {
-        if (!it->get()->hasTagName(dialogTag))
-            continue;
-        HTMLDialogElement* dialog = toHTMLDialogElement(it->get());
-        if (dialog->isModal())
-            return dialog;
-    }
-    return 0;
+    if (m_topLayerElements.isEmpty())
+        return 0;
+    return toHTMLDialogElement(m_topLayerElements.last().get());
 }
 
 void Document::webkitExitPointerLock()