clean up printing::Image and printing::Metafile

printing/emf_win.h

 // Copyright (c) 2012 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 PRINTING_EMF_WIN_H_
 #define PRINTING_EMF_WIN_H_
 
 #include <stddef.h>
 #include <stdint.h>
 #include <windows.h>
@@ skipping 59 matching lines @@
   bool FinishDocument() override;
 
   uint32_t GetDataSize() const override;
   bool GetData(void* buffer, uint32_t size) const override;
 
   // Should be passed to Playback to keep the exact same size.
   gfx::Rect GetPageBounds(unsigned int page_number) const override;
 
   unsigned int GetPageCount() const override;
   HDC context() const override;
-  bool Playback(HDC hdc, const RECT* rect) const override;
+
   bool SafePlayback(HDC hdc) const override;
 
+  // "Plays" the EMF buffer in a HDC. It is the same effect as calling the
+  // original GDI function that were called when recording the EMF. |rect| is in
+  // "logical units" and is optional. If |rect| is NULL, the natural EMF bounds
+  // are used.
+  // Note: Windows has been known to have stack buffer overflow in its GDI
+  // functions, whether used directly or indirectly through precompiled EMF
+  // data. We have to accept the risk here. Since it is used only for printing,
+  // it requires user intervention.
+  bool Playback(HDC hdc, const RECT* rect) const;
+
   HENHMETAFILE emf() const { return emf_; }
 
   // Returns true if metafile contains alpha blend.
   bool IsAlphaBlendUsed() const;
 
   // Returns new metafile with only bitmap created by playback of the current
   // metafile. Returns NULL if fails.
   std::unique_ptr<Emf> RasterizeMetafile(int raster_area_in_pixels) const;
 
   // Returns new metafile where AlphaBlend replaced by bitmaps. Returns NULL
@@ skipping 91 matching lines @@
   std::vector<Record> items_;
 
   EnumerationContext context_;
 
   DISALLOW_COPY_AND_ASSIGN(Enumerator);
 };
 
 }  // namespace printing
 
 #endif  // PRINTING_EMF_WIN_H_