Remove skia::PlatformBitmap.

skia/ext/platform_canvas.cc

 // 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.
 
 #include "skia/ext/platform_canvas.h"
 
 #include "skia/ext/bitmap_platform_device.h"
 #include "third_party/skia/include/core/SkTypes.h"
 
 namespace skia {
@@ skipping 40 matching lines @@
 
 SkCanvas* CreateCanvas(const skia::RefPtr<SkBaseDevice>& device, OnFailureType failureType) {
   if (!device) {
     if (CRASH_ON_FAILURE == failureType)
       SK_CRASH();
     return NULL;
   }
   return new SkCanvas(device.get());
 }
 
-PlatformBitmap::PlatformBitmap() : surface_(0), platform_extra_(0) {}
-
 }  // namespace skia