Change call-sites now that SkCanvas is not ref-counted

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 <stddef.h>
 #include <stdint.h>
 
@@ skipping 40 matching lines @@
 // static
 TransportDIB* TransportDIB::CreateWithHandle(Handle handle) {
   return new TransportDIB(handle);
 }
 
 // static
 bool TransportDIB::is_valid_handle(Handle dib) {
   return dib.IsValid();
 }
 
-SkCanvas* TransportDIB::GetPlatformCanvas(int w, int h,
-                                                      bool opaque) {
+std::unique_ptr<SkCanvas> TransportDIB::GetPlatformCanvas(int w,
+                                                          int h,
+                                                          bool opaque) {
   // This DIB already mapped the file into this process, but PlatformCanvas
   // will map it again.
   DCHECK(!memory()) << "Mapped file twice in the same process.";
 
   // We can't check the canvas size before mapping, but it's safe because
   // Windows will fail to map the section if the dimensions of the canvas
   // are too large.
-  SkCanvas* canvas = skia::CreatePlatformCanvas(
+  std::unique_ptr<SkCanvas> canvas = skia::CreatePlatformCanvas(
       w, h, opaque, shared_memory_.handle().GetHandle(),
       skia::RETURN_NULL_ON_FAILURE);
 
   // Calculate the size for the memory region backing the canvas.
   if (canvas)
     size_ = skia::PlatformCanvasStrideForWidth(w) * h;
 
   return canvas;
 }
 
@@ skipping 10 matching lines @@
     return false;
   }
 
   size_ = shared_memory_.mapped_size();
   return true;
 }
 
 void* TransportDIB::memory() const {
   return shared_memory_.memory();
 }