Implement a simple image cache for Sky in Dart (no eviction)

sky/engine/core/loader/CanvasImageLoader.h

 // SKY_ENGINE_CORE_PAINTING_CANVASIMAGE_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 SKY_ENGINE_CORE_LOADER_CANVASIMAGELOADER_H_
 #define SKY_ENGINE_CORE_LOADER_CANVASIMAGELOADER_H_
 
 #include "mojo/common/data_pipe_drainer.h"
 #include "sky/engine/core/loader/ImageLoaderCallback.h"
@@ skipping 10 matching lines @@
                           public RefCounted<CanvasImageLoader>,
                           public DartWrappable {
   DEFINE_WRAPPERTYPEINFO();
  public:
   static PassRefPtr<CanvasImageLoader> create(const String& src, PassOwnPtr<ImageLoaderCallback> callback)
   {
     return adoptRef(new CanvasImageLoader(src, callback));
   }
   virtual ~CanvasImageLoader();
 
-  void load();
-
   // MojoFetcher::Client
   void OnReceivedResponse(mojo::URLResponsePtr) override;
 
   // mojo::common::DataPipeDrainer::Client
   void OnDataAvailable(const void*, size_t) override;
   void OnDataComplete() override;
 
  private:
   explicit CanvasImageLoader(const String& src, PassOwnPtr<ImageLoaderCallback> callback);
 
   OwnPtr<MojoFetcher> fetcher_;
   OwnPtr<mojo::common::DataPipeDrainer> drainer_;
   RefPtr<SharedBuffer> buffer_;
-
-  KURL url_;
   OwnPtr<ImageLoaderCallback> callback_;
 };
 
 }  // namespace blink
 
 #endif  // SKY_ENGINE_CORE_LOADER_CANVASIMAGELOADER_H_