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

Source/core/paint/PartPainter.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 PartPainter_h
 #define PartPainter_h
 
+#include "wtf/Allocator.h"
+
 namespace blink {
 
 struct PaintInfo;
 class LayoutPoint;
 class LayoutPart;
 
 class PartPainter {
+    STACK_ALLOCATED();
 public:
     PartPainter(LayoutPart& layoutPart) : m_layoutPart(layoutPart) { }
 
     void paint(const PaintInfo&, const LayoutPoint&);
     void paintContents(const PaintInfo&, const LayoutPoint&);
 
 private:
     LayoutPart& m_layoutPart;
 };
 
 } // namespace blink
 
 #endif // PartPainter_h