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

cc/playback/discardable_image_map.h

 // Copyright 2015 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 CC_PLAYBACK_DISCARDABLE_IMAGE_MAP_H_
 #define CC_PLAYBACK_DISCARDABLE_IMAGE_MAP_H_
 
 #include <utility>
 #include <vector>
 
@@ skipping 18 matching lines @@
   class CC_EXPORT ScopedMetadataGenerator {
    public:
     ScopedMetadataGenerator(DiscardableImageMap* image_map,
                             const gfx::Size& bounds);
     ~ScopedMetadataGenerator();
 
     SkCanvas* canvas() { return metadata_canvas_.get(); }
 
    private:
     DiscardableImageMap* image_map_;
-    sk_sp<SkCanvas> metadata_canvas_;
+    std::unique_ptr<SkCanvas> metadata_canvas_;
   };
 
   DiscardableImageMap();
   ~DiscardableImageMap();
 
   bool empty() const { return all_images_.empty(); }
   void GetDiscardableImagesInRect(const gfx::Rect& rect,
                                   const gfx::SizeF& raster_scales,
                                   std::vector<DrawImage>* images) const;
 
  private:
   friend class ScopedMetadataGenerator;
   friend class DiscardableImageMapTest;
 
-  sk_sp<SkCanvas> BeginGeneratingMetadata(const gfx::Size& bounds);
+  std::unique_ptr<SkCanvas> BeginGeneratingMetadata(const gfx::Size& bounds);
   void EndGeneratingMetadata();
 
   std::vector<std::pair<DrawImage, gfx::Rect>> all_images_;
   RTree images_rtree_;
 };
 
 }  // namespace cc
 
 #endif  // CC_PLAYBACK_DISCARDABLE_IMAGE_MAP_H_