Remove duplicate typedef

skia/ext/platform_canvas.h

 // Copyright (c) 2011 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_H_
 #define SKIA_EXT_PLATFORM_CANVAS_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
 // The platform-specific device will include the necessary platform headers
 // to get the surface type.
 #include "build/build_config.h"
 #include "skia/ext/platform_surface.h"
 #include "skia/ext/refptr.h"
 #include "third_party/skia/include/core/SkBitmap.h"
 #include "third_party/skia/include/core/SkCanvas.h"
 #include "third_party/skia/include/core/SkPixelRef.h"
 #include "third_party/skia/include/core/SkPixmap.h"
 
 class SkBaseDevice;
 
+// A PlatformCanvas is a software-rasterized SkCanvas which is *also*
+// addressable by the platform-specific drawing API (GDI, Core Graphics,
+// Cairo...).
+
 namespace skia {
 
-typedef SkCanvas PlatformCanvas;
-
 //
 //  Note about error handling.
 //
 //  Creating a canvas can fail at times, most often because we fail to allocate
 //  the backing-store (pixels). This can be from out-of-memory, or something
 //  more opaque, like GDI or cairo reported a failure.
 //
 //  To allow the caller to handle the failure, every Create... factory takes an
 //  enum as its last parameter. The default value is kCrashOnFailure. If the
 //  caller passes kReturnNullOnFailure, then the caller is responsible to check
 //  the return result.
 //
 enum OnFailureType {
   CRASH_ON_FAILURE,
   RETURN_NULL_ON_FAILURE
 };
 
 #if defined(WIN32)
   // The shared_section parameter is passed to gfx::PlatformDevice::create.
   // See it for details.
   SK_API SkCanvas* CreatePlatformCanvas(int width,
                                         int height,
                                         bool is_opaque,
                                         HANDLE shared_section,
                                         OnFailureType failure_type);
 
   // Draws the top layer of the canvas into the specified HDC. Only works
-  // with a PlatformCanvas with a BitmapPlatformDevice.
+  // with a SkCanvas with a BitmapPlatformDevice.
   SK_API void DrawToNativeContext(SkCanvas* canvas,
                                   HDC hdc,
                                   int x,
                                   int y,
                                   const RECT* src_rect);
 #elif defined(__APPLE__)
   SK_API SkCanvas* CreatePlatformCanvas(CGContextRef context,
                                         int width,
                                         int height,
                                         bool is_opaque,
@@ skipping 120 matching lines @@
 SK_API bool IsPreviewMetafile(const SkCanvas& canvas);
 
 // Returns the CGContext that backing the SkCanvas.
 // Returns NULL if none is bound.
 SK_API CGContextRef GetBitmapContext(const SkCanvas& canvas);
 #endif
 
 }  // namespace skia
 
 #endif  // SKIA_EXT_PLATFORM_CANVAS_H_