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

ui/surface/transport_dib_win.cc

 // 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.
 
 #include "ui/surface/transport_dib.h"
 
 #include <windows.h>
 
 #include <limits>
 
@@ skipping 52 matching lines @@
 // static
 bool TransportDIB::is_valid_id(TransportDIB::Id id) {
   return is_valid_handle(id.handle);
 }
 
 skia::PlatformCanvas* TransportDIB::GetPlatformCanvas(int w, int h) {
   // This DIB already mapped the file into this process, but PlatformCanvas
   // will map it again.
   DCHECK(!memory()) << "Mapped file twice in the same process.";
 
-  scoped_ptr<skia::PlatformCanvas> canvas(new skia::PlatformCanvas);
-  if (!canvas->initialize(w, h, true, handle()))
-    return NULL;
-  return canvas.release();
+  return skia::CreatePlatformCanvas(w, h, true, handle(),
+                                    skia::RETURN_NULL_ON_FAILURE);
 }
 
 bool TransportDIB::Map() {
   if (!is_valid_handle(handle()))
     return false;
   if (memory())
     return true;
 
   if (!shared_memory_.Map(0 /* map whole shared memory segment */)) {
     LOG(ERROR) << "Failed to map transport DIB"
@@ skipping 14 matching lines @@
   return shared_memory_.memory();
 }
 
 TransportDIB::Handle TransportDIB::handle() const {
   return shared_memory_.handle();
 }
 
 TransportDIB::Id TransportDIB::id() const {
   return Id(handle(), sequence_num_);
 }