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

Source/core/editing/EditingBehavior.h

Index: Source/core/editing/EditingBehavior.h
diff --git a/Source/core/editing/EditingBehavior.h b/Source/core/editing/EditingBehavior.h
index dfad75a564b6d3ca6e9804d82cb34d416aced055..2a500e342e7c928aea1d43da2a862f95757a8cb2 100644
--- a/Source/core/editing/EditingBehavior.h
+++ b/Source/core/editing/EditingBehavior.h
@@ -23,12 +23,13 @@
 
 #include "core/CoreExport.h"
 #include "core/editing/EditingBehaviorTypes.h"
+#include "wtf/Allocator.h"
 
 namespace blink {
 class KeyboardEvent;
 
 class CORE_EXPORT EditingBehavior {
-
+    STACK_ALLOCATED();
 public:
     explicit EditingBehavior(EditingBehaviorType type)
         : m_type(type)