Simplify platform_canvas.h by recognizing that PlatformCanvas does not actually extend

ui/surface/transport_dib.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 UI_SURFACE_TRANSPORT_DIB_H_
 #define UI_SURFACE_TRANSPORT_DIB_H_
 
 #include "base/basictypes.h"
 #include "ui/surface/surface_export.h"
 
 #if defined(OS_WIN) || defined(OS_MACOSX) || defined(OS_ANDROID)
 #include "base/shared_memory.h"
 #endif
 
 #if defined(OS_WIN)
 #include <windows.h>
 #elif defined(USE_X11)
 #include "ui/base/x/x11_util.h"
 #endif
 
-namespace skia {
-class PlatformCanvas;
-}
+class SkCanvas;
 
 // -----------------------------------------------------------------------------
 // A TransportDIB is a block of memory that is used to transport pixels
 // between processes: from the renderer process to the browser, and
 // between renderer and plugin processes.
 // -----------------------------------------------------------------------------
 class SURFACE_EXPORT TransportDIB {
  public:
   ~TransportDIB();
 
@@ skipping 127 matching lines @@
   // Returns a canvas using the memory of this TransportDIB. The returned
   // pointer will be owned by the caller. The bitmap will be of the given size,
   // which should fit inside this memory.
   //
   // On POSIX, this |TransportDIB| will be mapped if not already. On Windows,
   // this |TransportDIB| will NOT be mapped and should not be mapped prior,
   // because PlatformCanvas will map the file internally.
   //
   // Will return NULL on allocation failure. This could be because the image
   // is too large to map into the current process' address space.
-  skia::PlatformCanvas* GetPlatformCanvas(int w, int h);
+  SkCanvas* GetPlatformCanvas(int w, int h);
 
   // Map the DIB into the current process if it is not already. This is used to
   // map a DIB that has already been created. Returns true if the DIB is mapped.
   bool Map();
 
   // Return a pointer to the shared memory.
   void* memory() const;
 
   // Return the maximum size of the shared memory. This is not the amount of
   // data which is valid, you have to know that via other means, this is simply
@@ skipping 36 matching lines @@
   Display* display_;  // connection to the X server
   size_t inflight_counter_;  // How many requests to the X server are in flight
   bool detached_;  // If true, delete the transport DIB when it is idle
 #endif
   size_t size_;  // length, in bytes
 
   DISALLOW_COPY_AND_ASSIGN(TransportDIB);
 };
 
 #endif  // UI_SURFACE_TRANSPORT_DIB_H_