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

components/image_fetcher/image_data_fetcher.cc

+// 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.
+
+#include "components/image_fetcher/image_data_fetcher.h"
+
+#include "net/base/load_flags.h"
+#include "net/url_request/url_fetcher.h"
+#include "net/url_request/url_fetcher_delegate.h"
+#include "net/url_request/url_request.h"
+#include "net/url_request/url_request_context_getter.h"
+#include "net/url_request/url_request_status.h"
+#include "url/gurl.h"
+
+namespace image_fetcher {
+
+// An active image URL fetcher request. The class contains any related request
+// state and logic for handling a single image url request.
+class ImageDataFetcher::ImageDataFetcherRequest
+    : public net::URLFetcherDelegate {
+ public:
+  ImageDataFetcherRequest(const GURL& url,
+                          const ImageDataFetcherCallback& callback,
+                          ImageDataFetcher* image_url_fetcher);
+  ~ImageDataFetcherRequest() override {}
+
+  // Sends the URL requests.
+  void Start(net::URLRequestContextGetter* request_context);
+
+ private:
+  // Method inherited from URLFetcherDelegate
+  void OnURLFetchComplete(const net::URLFetcher* source) override;
+
+  // The URL of the image to fetch.
+  const GURL url_;
+
+  // The callback to run after the image data was fetched. The callback will
+  // be run even if the image data could not be fetched successfully.
+  ImageDataFetcherCallback callback_;
+
+  // The ImageDataFetcher that owns the ImageDataFetcherRequest.
+  ImageDataFetcher* image_url_fetcher_;
+
+  std::unique_ptr<net::URLFetcher> url_fetcher_;
+
+  DISALLOW_COPY_AND_ASSIGN(ImageDataFetcherRequest);
+};
+
+ImageDataFetcher::ImageDataFetcherRequest::ImageDataFetcherRequest(
+    const GURL& url,
+    const ImageDataFetcherCallback& callback,
+    ImageDataFetcher* image_url_fetcher)
+    : url_(url),
+      callback_(callback),
+      image_url_fetcher_(image_url_fetcher) {
+}
+
+void ImageDataFetcher::ImageDataFetcherRequest::Start(
+    net::URLRequestContextGetter* request_context) {
+  DCHECK(!url_fetcher_);
+
+  url_fetcher_ = net::URLFetcher::Create(url_, net::URLFetcher::GET, this);
+  url_fetcher_->SetRequestContext(request_context);
+  url_fetcher_->Start();
+}
+
+void ImageDataFetcher::ImageDataFetcherRequest::OnURLFetchComplete(
+    const net::URLFetcher* source) {
+  // An empty string is passed to the callback in case on an unsuccessfull URL
+  // request.
+  std::string image_data;
+  if (source->GetStatus().status() == net::URLRequestStatus::SUCCESS) {
+    source->GetResponseAsString(&image_data);
+  }
+  callback_.Run(image_data);
+
+  // Remove the completed ImageDataFetcherRequest from the internal request
+  // queue. This must be last in the method.
+  image_url_fetcher_->RemoveImageDataFetcherRequest(url_);
+}
+
+ImageDataFetcher::ImageDataFetcher(
+    net::URLRequestContextGetter* url_request_context_getter)
+    : url_request_context_getter_(url_request_context_getter) {}
+
+ImageDataFetcher::~ImageDataFetcher() {}
+
+void ImageDataFetcher::FetchImageData(
+    const GURL& url, const ImageDataFetcherCallback& callback) {
+  std::unique_ptr<ImageDataFetcherRequest> request(
+      new ImageDataFetcherRequest(url, callback, this));
+  request->Start(url_request_context_getter_.get());
+  pending_requests_[url] = std::move(request);
+}
+
+void ImageDataFetcher::RemoveImageDataFetcherRequest(const GURL& image_url) {
+  size_t count = pending_requests_.erase(image_url);
+  DCHECK(count);
+}
+
+}  // namespace image_fetcher