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

Source/core/editing/iterators/BitStack.h

Index: Source/core/editing/iterators/BitStack.h
diff --git a/Source/core/editing/iterators/BitStack.h b/Source/core/editing/iterators/BitStack.h
index 03077d51047a9c884254e1d87a5a7a8c525ba635..f588fa54441f95ec013d489170d7eb9b89e5c23a 100644
--- a/Source/core/editing/iterators/BitStack.h
+++ b/Source/core/editing/iterators/BitStack.h
@@ -27,6 +27,7 @@
 #define BitStack_h
 
 #include "core/CoreExport.h"
+#include "wtf/Allocator.h"
 #include "wtf/Vector.h"
 
 namespace blink {
@@ -34,6 +35,7 @@ namespace blink {
 class Node;
 
 class CORE_EXPORT BitStack {
+    STACK_ALLOCATED();
 public:
     BitStack();
     ~BitStack();