Reland: Split the code for fetching images and for decoding images into two separate classes. This w

components/image_fetcher/image_decoder.h

Index: components/image_fetcher/image_decoder.h
diff --git a/components/image_fetcher/image_decoder.h b/components/image_fetcher/image_decoder.h
new file mode 100644
index 0000000000000000000000000000000000000000..3a90c57e581107ac5b9130de1f76499c15d7933d
--- /dev/null
+++ b/components/image_fetcher/image_decoder.h
@@ -0,0 +1,37 @@
+// Copyright 2016 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 COMPONENTS_IMAGE_FETCHER_IMAGE_DECODER_H_
+#define COMPONENTS_IMAGE_FETCHER_IMAGE_DECODER_H_
+
+#include <string>
+#include "base/callback_forward.h"
+
+namespace gfx {
+class Image;
+}  // namespace gfx
+
+namespace image_fetcher {
+
+using ImageDecodedCallback = base::Callback<void(const gfx::Image&)>;
+
+// ImageDecoder defines the common interface for decoding images.
+class ImageDecoder {
+ public:
+  ImageDecoder() {}
+  virtual ~ImageDecoder() {}
+
+  // Decodes the passed |image_data| and runs the given callback. The callback
+  // is run even if decoding the image fails. In case an error occured during
+  // decoding the image an empty image is passed to the callback.
+  virtual void DecodeImage(const std::string& image_data,
+                           const ImageDecodedCallback& callback) = 0;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(ImageDecoder);
+};
+
+}  // namespace image_fetcher
+
+#endif  // COMPONENTS_IMAGE_FETCHER_IMAGE_DECODER_H_