Refactor the PlatformContext layer to have only one class.

skia/ext/platform_canvas_mac.h

-// Copyright (c) 2006-2008 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_PLATFORM_CANVAS_MAC_H_
-#define SKIA_EXT_PLATFORM_CANVAS_MAC_H_
-
-#include "skia/ext/platform_device_mac.h"
-
-#include "third_party/skia/include/core/SkCanvas.h"
-
-namespace skia {
-
-// This class is a specialization of the regular SkCanvas that is designed to
-// work with a gfx::PlatformDevice to manage platform-specific drawing. It
-// allows using both Skia operations and platform-specific operations.
-class PlatformCanvasMac : public SkCanvas {
- public:
-  // Set is_opaque if you are going to erase the bitmap and not use
-  // tranparency: this will enable some optimizations.  The shared_section
-  // parameter is passed to gfx::PlatformDevice::create.  See it for details.
-  //
-  // If you use the version with no arguments, you MUST call initialize()
-  PlatformCanvasMac();
-  PlatformCanvasMac(int width, int height, bool is_opaque);
-  PlatformCanvasMac(int width, int height, bool is_opaque,
-                    CGContextRef context);
-  PlatformCanvasMac(int width, int height, bool is_opaque,
-                    uint8_t* context);
-  virtual ~PlatformCanvasMac();
-
-  // For two-part init, call if you use the no-argument constructor above
-  bool initialize(int width, int height, bool is_opaque);
-  bool initialize(int width, int height, bool is_opaque, uint8_t* data);
-
-  // These calls should surround calls to platform drawing routines. The CG
-  // context returned by beginPlatformPaint is the one that can be used to
-  // draw into.
-  // Call endPlatformPaint when you are done and want to use Skia operations
-  // again; this will synchronize the bitmap.
-  virtual CGContextRef beginPlatformPaint();
-  virtual void endPlatformPaint();
-
-  // Returns the platform device pointer of the topmost rect with a non-empty
-  // clip. In practice, this is usually either the top layer or nothing, since
-  // we usually set the clip to new layers when we make them.
-  //
-  // If there is no layer that is not all clipped out, this will return a
-  // dummy device so callers do not have to check. If you are concerned about
-  // performance, check the clip before doing any painting.
-  //
-  // This is different than SkCanvas' getDevice, because that returns the
-  // bottommost device.
-  //
-  // Danger: the resulting device should not be saved. It will be invalidated
-  // by the next call to save() or restore().
-  PlatformDeviceMac& getTopPlatformDevice() const;
-
-  // Allow callers to see the non-virtual function even though we have an
-  // override of a virtual one.
-  using SkCanvas::clipRect;
-
-  // Return the stride (length of a line in bytes) for the given width. Because
-  // we use 32-bits per pixel, this will be roughly 4*width. However, for
-  // alignment reasons we may wish to increase that.
-  static size_t StrideForWidth(unsigned width);
-
- protected:
-  // Creates a device store for use by the canvas. We override this so that
-  // the device is always our own so we know that we can use GDI operations
-  // on it. Simply calls into createPlatformDevice().
-  virtual SkDevice* createDevice(SkBitmap::Config, int width, int height,
-                                 bool is_opaque, bool isForLayer);
-
-  // Creates a device store for use by the canvas. By default, it creates a
-  // BitmapPlatformDevice object. Can be overridden to change the object type.
-  virtual SkDevice* createPlatformDevice(int width, int height, bool is_opaque,
-                                         CGContextRef context);
-
- private:
-  // Unimplemented. This is to try to prevent people from calling this function
-  // on SkCanvas. SkCanvas' version is not virtual, so we can't prevent this
-  // 100%, but hopefully this will make people notice and not use the function.
-  // Calling SkCanvas' version will create a new device which is not compatible
-  // with us and we will crash if somebody tries to draw into it with
-  // CoreGraphics.
-  SkDevice* setBitmapDevice(const SkBitmap& bitmap);
-
-  // Disallow copy and assign.
-  PlatformCanvasMac(const PlatformCanvasMac&);
-  PlatformCanvasMac& operator=(const PlatformCanvasMac&);
-};
-
-}  // namespace skia
-
-#endif  // SKIA_EXT_PLATFORM_CANVAS_MAC_H_