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

Source/core/dom/shadow/ComposedTreeTraversal.h

Index: Source/core/dom/shadow/ComposedTreeTraversal.h
diff --git a/Source/core/dom/shadow/ComposedTreeTraversal.h b/Source/core/dom/shadow/ComposedTreeTraversal.h
index 9026c58e7a41e42bbd930626d6f08a1cbdc11cd6..ebc792a55317ac33626663a3f0a211dcd0295ff6 100644
--- a/Source/core/dom/shadow/ComposedTreeTraversal.h
+++ b/Source/core/dom/shadow/ComposedTreeTraversal.h
@@ -32,6 +32,7 @@
 #include "core/dom/LayoutTreeBuilderTraversal.h"
 #include "core/dom/shadow/InsertionPoint.h"
 #include "core/dom/shadow/ShadowRoot.h"
+#include "wtf/Allocator.h"
 
 namespace blink {
 
@@ -49,6 +50,7 @@ class Node;
 // FIXME: Make some functions inline to optimise the performance.
 // https://bugs.webkit.org/show_bug.cgi?id=82702
 class CORE_EXPORT ComposedTreeTraversal {
+    STATIC_ONLY(ComposedTreeTraversal);
 public:
     typedef LayoutTreeBuilderTraversal::ParentDetails ParentTraversalDetails;