Clarify FullscreenElementStack::addDocumentToFullScreenChangeEventQueue

Source/core/dom/FullscreenElementStack.cpp

Index: Source/core/dom/FullscreenElementStack.cpp
diff --git a/Source/core/dom/FullscreenElementStack.cpp b/Source/core/dom/FullscreenElementStack.cpp
index 239fe6a6a818725700a660821d6efb5922a8b9b2..30f945dbd12d6969d4363d71113616e005d3de34 100644
--- a/Source/core/dom/FullscreenElementStack.cpp
+++ b/Source/core/dom/FullscreenElementStack.cpp
@@ -566,13 +566,12 @@ void FullscreenElementStack::pushFullscreenElementStack(Element& element)
 
 void FullscreenElementStack::addDocumentToFullScreenChangeEventQueue(Document& doc)
 {
-    Node* target = 0;
-    if (FullscreenElementStack* fullscreen = fromIfExists(doc)) {
-        target = fullscreen->webkitFullscreenElement();
-        if (!target)
-            target = fullscreen->webkitCurrentFullScreenElement();
-    }
+    ASSERT(doc.hasFullscreenElementStack());
+    FullscreenElementStack& fullscreen = from(doc);
 
+    Node* target = fullscreen.webkitFullscreenElement();
+    if (!target)
+        target = fullscreen.webkitCurrentFullScreenElement();
     if (!target)
         target = &doc;
     m_fullScreenChangeEventTargetQueue.append(target);