Split the code for fetching images and for decoding images into two separate classes. This will all…

components/image_fetcher/image_data_fetcher.h

Index: components/image_fetcher/image_data_fetcher.h
diff --git a/components/image_fetcher/image_data_fetcher.h b/components/image_fetcher/image_data_fetcher.h
new file mode 100644
index 0000000000000000000000000000000000000000..5cfea41f62fa2c20a157f46c2c3ffd0865a0199e
--- /dev/null
+++ b/components/image_fetcher/image_data_fetcher.h
@@ -0,0 +1,54 @@
+// 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 "base/macros.h"
+#include "net/url_request/url_fetcher.h"
+#include "net/url_request/url_fetcher_delegate.h"
+#include "net/url_request/url_request.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)>;
+
+  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 FetchImageURL(const GURL& image_url,

[Marc Treib, 2016/06/10 08:32:37]

FetchImageData?

[markusheintz_, 2016/06/10 09:43:14]

Already done. Sorry I forgot last night and quickly did it this morning in a
separate patchset

+                     const ImageDataFetcherCallback& callback);
+
+ private:
+  class ImageDataFetcherRequest;

[Marc Treib, 2016/06/10 08:32:37]

optional: Since this is a private inner class, you could also just call it
Request?

[markusheintz_, 2016/06/10 09:43:14]

Acknowledged.

+
+  // 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>> request_queue_;

[Marc Treib, 2016/06/10 08:32:37]

Just requests_, or maybe pending_requests_? It's not actually a queue.

[markusheintz_, 2016/06/10 09:43:14]

I chose pending_requests_. 

+
+  net::URLRequestContextGetter* url_request_context_getter_;
+
+  DISALLOW_COPY_AND_ASSIGN(ImageDataFetcher);
+};
+
+}  // namespace image_fetcher
+
+#endif  // COMPONENTS_IMAGE_FETCHER_IMAGE_DATA_FETCHER_H_