Move image loading out of C++ into Dart

sky/engine/core/loader/ImageLoaderCallback.h

Index: sky/engine/core/loader/ImageLoaderCallback.h
diff --git a/sky/engine/core/loader/ImageLoaderCallback.h b/sky/engine/core/loader/ImageLoaderCallback.h
deleted file mode 100644
index 036c20610234b21ee04354b75c2246e844c58b6d..0000000000000000000000000000000000000000
--- a/sky/engine/core/loader/ImageLoaderCallback.h
+++ /dev/null
@@ -1,20 +0,0 @@
-// 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_IMAGELOADERCALLBACK_H_
-#define SKY_ENGINE_CORE_LOADER_IMAGELOADERCALLBACK_H_
-
-#include "sky/engine/core/painting/CanvasImage.h"
-
-namespace blink {
-
-class ImageLoaderCallback {
-public:
-    virtual ~ImageLoaderCallback() {}
-    virtual void handleEvent(CanvasImage* result) = 0;
-};
-
-} // namespace blink
-
-#endif  // SKY_ENGINE_CORE_LOADER_IMAGELOADERCALLBACK_H_