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

Source/core/layout/PendingSelection.h

Index: Source/core/layout/PendingSelection.h
diff --git a/Source/core/layout/PendingSelection.h b/Source/core/layout/PendingSelection.h
index c61352da71133fcee77d9a322e32fa3fb94e0f61..18b7ee757a0bbcdc521cb7cf4142549c7d3f79bd 100644
--- a/Source/core/layout/PendingSelection.h
+++ b/Source/core/layout/PendingSelection.h
@@ -24,6 +24,7 @@
 
 #include "core/editing/Position.h"
 #include "core/editing/VisibleSelection.h"
+#include "platform/heap/Handle.h"
 
 namespace blink {
 
@@ -31,6 +32,7 @@ class Document;
 class FrameSelection;
 
 class PendingSelection final : public NoBaseWillBeGarbageCollected<PendingSelection> {
+    WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED(PendingSelection);
 public:
     static PassOwnPtrWillBeRawPtr<PendingSelection> create()
     {