Implement manifest icon downloader

chrome/browser/manifest/manifest_icon_downloader.h

+// 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 CHROME_BROWSER_MANIFEST_MANIFEST_ICON_DOWNLOADER_H_
+#define CHROME_BROWSER_MANIFEST_MANIFEST_ICON_DOWNLOADER_H_
+
+#include <vector>
+
+#include "base/basictypes.h"
+#include "base/callback_forward.h"
+#include "third_party/skia/include/core/SkBitmap.h"
+
+namespace content {
+class WebContents;
+}  // namespace content
+
+namespace gfx {
+class Size;
+}  // namespace gfx
+
+class GURL;
+
+// Helper class which downloads the icon located at a specified. If the icon
+// file contains multiple icons then it attempts to pick the one closest in size
+// bigger than or equal to ideal_icon_size_in_dp, taking into account the
+// density of the device. If a bigger icon is chosen then, the icon is scaled
+// down to be equal to ideal_icon_size_in_dp.
+class ManifestIconDownloader final {
+ public:
+  using IconFetchCallback = base::Callback<void(const SkBitmap&)>;
+
+  ManifestIconDownloader() = delete;
+  ~ManifestIconDownloader() = delete;
+
+  // Returns whether the download has started.
+  // It will return false if the current context or information do not allow to
+  // download the image.
+  static bool Download(content::WebContents* web_contents,
+                       const GURL& icon_url,
+                       int ideal_icon_size_in_dp,
+                       const IconFetchCallback& callback);
+
+ private:
+  // Callback run after the manifest icon downloaded successfully or the
+  // download failed.
+  static void OnIconFetched(int ideal_icon_size_in_px,
+                            int minimum_icon_size_in_px,
+                            const IconFetchCallback& callback,
+                            int id,
+                            int http_status_code,
+                            const GURL& url,
+                            const std::vector<SkBitmap>& bitmaps,
+                            const std::vector<gfx::Size>& sizes);
+
+  static void ScaleIcon(int ideal_icon_size_in_px,
+                        const SkBitmap& bitmap,
+                        const IconFetchCallback& callback);
+
+  static int FindClosestBitmapIndex(int ideal_icon_size_in_px,
+                                    int minimum_icon_size_in_px,
+                                    const std::vector<SkBitmap>& bitmaps);
+
+  friend class ManifestIconDownloaderTest;
+
+  DISALLOW_COPY_AND_ASSIGN(ManifestIconDownloader);
+};
+
+#endif  // CHROME_BROWSER_MANIFEST_MANIFEST_ICON_DOWNLOADER_H_