Make classes and structures in core/dom fast-allocated.

Source/core/dom/DocumentFullscreen.h

Index: Source/core/dom/DocumentFullscreen.h
diff --git a/Source/core/dom/DocumentFullscreen.h b/Source/core/dom/DocumentFullscreen.h
index d522b0300c76492bba627e8265a2614936c2069c..c8ef1e8d8af6d46670dd75979fec17478ed4f005 100644
--- a/Source/core/dom/DocumentFullscreen.h
+++ b/Source/core/dom/DocumentFullscreen.h
@@ -27,6 +27,7 @@
 #define DocumentFullscreen_h
 
 #include "core/events/EventTarget.h"
+#include "wtf/Allocator.h"
 
 namespace blink {
 
@@ -34,6 +35,7 @@ class Document;
 class Element;
 
 class DocumentFullscreen {
+    STATIC_ONLY(DocumentFullscreen);
 public:
     static bool fullscreenEnabled(Document&);
     static Element* fullscreenElement(Document&);