Revert of Delete Mac & Cairo skia::BitmapPlatformDevice impls

skia/ext/platform_device.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 SKIA_EXT_PLATFORM_DEVICE_H_
 #define SKIA_EXT_PLATFORM_DEVICE_H_
 
 #include "build/build_config.h"
 
 #include "skia/ext/native_drawing_context.h"
@@ skipping 28 matching lines @@
 //
 // PlatformDevice provides an interface which sub-classes of SkBaseDevice can 
 // also provide to allow for drawing by the native platform into the device.
 // TODO(robertphillips): Once the bitmap-specific entry points are removed
 // from SkBaseDevice it might make sense for PlatformDevice to be derived
 // from it.
 class SK_API PlatformDevice {
  public:
   virtual ~PlatformDevice();
 
-// Only implemented in bitmap_platform_device_win.
-#if defined(WIN32)
   // The DC that corresponds to the bitmap, used for GDI operations drawing
   // into the bitmap. This is possibly heavyweight, so it should be existant
   // only during one pass of rendering.
   virtual NativeDrawingContext BeginPlatformPaint(const SkMatrix& transform,
                                                   const SkIRect& clip_bounds) = 0;
-#endif
 };
 
 }  // namespace skia
 
 #endif  // SKIA_EXT_PLATFORM_DEVICE_H_