Oilpan: tidy up definition of some stack-allocated scope objects.

Source/core/editing/InputMethodController.h

 /*
  * Copyright (C) 2006, 2007, 2008 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 68 matching lines @@
     void clear();
 
     PlainTextRange getSelectionOffsets() const;
     // Returns true if setting selection to specified offsets, otherwise false.
     bool setEditableSelectionOffsets(const PlainTextRange&);
     void extendSelectionAndDelete(int before, int after);
 
 private:
     class SelectionOffsetsScope {
         WTF_MAKE_NONCOPYABLE(SelectionOffsetsScope);
+        STACK_ALLOCATED();
     public:
-        SelectionOffsetsScope(InputMethodController*);
+        explicit SelectionOffsetsScope(InputMethodController*);
         ~SelectionOffsetsScope();
     private:
-        InputMethodController* m_inputMethodController;
+        RawPtrWillBeMember<InputMethodController> m_inputMethodController;
         const PlainTextRange m_offsets;
     };
     friend class SelectionOffsetsScope;
 
     RawPtrWillBeMember<LocalFrame> m_frame;
     RefPtrWillBeMember<Text> m_compositionNode;
     // We don't use PlainTextRange which is immutable, for composition range.
     unsigned m_compositionStart;
     unsigned m_compositionEnd;
     // startOffset and endOffset of CompositionUnderline are based on
@@ skipping 13 matching lines @@
     void selectComposition() const;
     enum FinishCompositionMode { ConfirmComposition, CancelComposition };
     // Returns true if composition exists.
     bool finishComposition(const String&, FinishCompositionMode);
     bool setSelectionOffsets(const PlainTextRange&);
 };
 
 } // namespace blink
 
 #endif // InputMethodController_h