Make Fullscreen::fullyExitFullscreen() static

Source/core/dom/Fullscreen.cpp

Index: Source/core/dom/Fullscreen.cpp
diff --git a/Source/core/dom/Fullscreen.cpp b/Source/core/dom/Fullscreen.cpp
index 75ae8baac46305c9e391c2124201c6777be581d9..58f7605634c7aa09bec279a13ab9487b2d73a45a 100644
--- a/Source/core/dom/Fullscreen.cpp
+++ b/Source/core/dom/Fullscreen.cpp
@@ -295,12 +295,12 @@ void Fullscreen::requestFullscreen(Element& element, RequestType requestType)
     enqueueErrorEvent(element, requestType);
 }
 
-void Fullscreen::fullyExitFullscreen()
+void Fullscreen::fullyExitFullscreen(Document& document)
 {
     // To fully exit fullscreen, run these steps:
 
     // 1. Let |doc| be the top-level browsing context's document.
-    Document& doc = document()->topDocument();
+    Document& doc = document.topDocument();
 
     // 2. If |doc|'s fullscreen element stack is empty, terminate these steps.
     if (!fullscreenElementFrom(doc))