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

Source/core/paint/FieldsetPainter.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef FieldsetPainter_h
 #define FieldsetPainter_h
 
+#include "wtf/Allocator.h"
+
 namespace blink {
 
 struct PaintInfo;
 class LayoutPoint;
 class LayoutFieldset;
 
 class FieldsetPainter {
+    STACK_ALLOCATED();
 public:
     FieldsetPainter(LayoutFieldset& layoutFieldset) : m_layoutFieldset(layoutFieldset) { }
 
     void paintBoxDecorationBackground(const PaintInfo&, const LayoutPoint&);
     void paintMask(const PaintInfo&, const LayoutPoint&);
 
 private:
     LayoutFieldset& m_layoutFieldset;
 };
 
 } // namespace blink
 
 #endif // FieldsetPainter_h