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

components/image_fetcher/image_data_fetcher.h

+// 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_DATA_FETCHER_H_
+#define COMPONENTS_IMAGE_FETCHER_IMAGE_DATA_FETCHER_H_
+
+#include <map>
+#include <memory>
+#include <string>
+
+#include "base/callback.h"
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+#include "url/gurl.h"
+
+namespace net {
+class URLRequestContextGetter;
+}  // namespace net
+
+namespace image_fetcher {
+
+class ImageDataFetcher {
+ public:
+  using ImageDataFetcherCallback =
+      base::Callback<void(const std::string& image_data)>;
+
+  explicit ImageDataFetcher(
+      net::URLRequestContextGetter* url_request_context_getter);
+  ~ImageDataFetcher();
+
+  // Fetches the raw image bytes from the given |image_url| and calls the given
+  // |callback|. The callback is run even if fetching the URL fails. In case
+  // of an error an empty string is passed to the callback.
+  void FetchImageData(const GURL& image_url,
+                      const ImageDataFetcherCallback& callback);
+
+ private:
+  class ImageDataFetcherRequest;
+
+  // Removes the ImageDataFetcherRequest for the given |image_url| from the
+  // internal request queue.
+  void RemoveImageDataFetcherRequest(const GURL& image_url);
+
+  // All active image url requests.
+  std::map<const GURL, std::unique_ptr<ImageDataFetcherRequest>>
+      pending_requests_;
+
+  scoped_refptr<net::URLRequestContextGetter> url_request_context_getter_;
+
+  DISALLOW_COPY_AND_ASSIGN(ImageDataFetcher);
+};
+
+}  // namespace image_fetcher
+
+#endif  // COMPONENTS_IMAGE_FETCHER_IMAGE_DATA_FETCHER_H_