Limit manual control of platform painting

skia/ext/bitmap_platform_device_skia.h

 // Copyright 2013 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 SKIA_EXT_BITMAP_PLATFORM_DEVICE_SKIA_H_
 #define SKIA_EXT_BITMAP_PLATFORM_DEVICE_SKIA_H_
 
 #include <stdint.h>
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
+#include "skia/ext/platform_canvas.h"
 #include "skia/ext/platform_device.h"
 
 namespace skia {
 
 // -----------------------------------------------------------------------------
 // For now we just use SkBitmap for SkBitmapDevice
 //
 // This is all quite ok for test_shell. In the future we will want to use
 // shared memory between the renderer and the main process at least. In this
 // case we'll probably create the buffer from a precreated region of memory.
@@ skipping 10 matching lines @@
   static BitmapPlatformDevice* Create(int width, int height, bool is_opaque,
                                       uint8_t* data);
 
   // Create a BitmapPlatformDevice from an already constructed bitmap;
   // you should probably be using Create(). This may become private later if
   // we ever have to share state between some native drawing UI and Skia, like
   // the Windows and Mac versions of this class do.
   explicit BitmapPlatformDevice(const SkBitmap& other);
   ~BitmapPlatformDevice() override;
 
+ protected:
   PlatformSurface BeginPlatformPaint() override;
 
- protected:
   SkBaseDevice* onCreateDevice(const CreateInfo&, const SkPaint*) override;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(BitmapPlatformDevice);
+
+  friend class skia::ScopedPlatformPaint;
 };
 
 }  // namespace skia
 
 #endif  // SKIA_EXT_BITMAP_PLATFORM_DEVICE_SKIA_H_