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

Source/core/editing/iterators/FullyClippedStateStack.h

Index: Source/core/editing/iterators/FullyClippedStateStack.h
diff --git a/Source/core/editing/iterators/FullyClippedStateStack.h b/Source/core/editing/iterators/FullyClippedStateStack.h
index 78cc5193c3e9f0d630ddd2f008f086da3b5c074c..74d5b607ac68e1f65aff0ab4771bc11fdfb71e9e 100644
--- a/Source/core/editing/iterators/FullyClippedStateStack.h
+++ b/Source/core/editing/iterators/FullyClippedStateStack.h
@@ -7,11 +7,13 @@
 
 #include "core/editing/EditingStrategy.h"
 #include "core/editing/iterators/BitStack.h"
+#include "wtf/Allocator.h"
 
 namespace blink {
 
 template<typename Strategy>
-class FullyClippedStateStackAlgorithm : public BitStack {
+class FullyClippedStateStackAlgorithm final : public BitStack {
+    STACK_ALLOCATED();
 public:
     FullyClippedStateStackAlgorithm();
     ~FullyClippedStateStackAlgorithm();