[part 1] Make classes and structures in modules/ fast-allocated.

Source/modules/filesystem/DataTransferItemFileSystem.h

Index: Source/modules/filesystem/DataTransferItemFileSystem.h
diff --git a/Source/modules/filesystem/DataTransferItemFileSystem.h b/Source/modules/filesystem/DataTransferItemFileSystem.h
index 7d9ebacfb417b9e3a7d25163a41f84b8a9ee421a..747ebe2048cfb0aa5b7ea3bee959c4d08c64545c 100644
--- a/Source/modules/filesystem/DataTransferItemFileSystem.h
+++ b/Source/modules/filesystem/DataTransferItemFileSystem.h
@@ -32,6 +32,7 @@
 #define DataTransferItemFileSystem_h
 
 #include "platform/heap/Handle.h"
+#include "wtf/Allocator.h"
 
 namespace blink {
 
@@ -40,12 +41,9 @@ class Entry;
 class ExecutionContext;
 
 class DataTransferItemFileSystem {
+    STATIC_ONLY(DataTransferItemFileSystem);
 public:
     static Entry* webkitGetAsEntry(ExecutionContext*, DataTransferItem&);
-
-private:
-    DataTransferItemFileSystem();
-    ~DataTransferItemFileSystem();
 };
 
 } // namespace blink