Extend LargeIconService to fetch missing favicons from a Google server

components/favicon/core/large_icon_service.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 COMPONENTS_FAVICON_CORE_LARGE_ICON_SERVICE_H_
 #define COMPONENTS_FAVICON_CORE_LARGE_ICON_SERVICE_H_
 
 #include <vector>
 
 #include "base/macros.h"
 #include "base/task/cancelable_task_tracker.h"
 #include "components/favicon_base/favicon_callback.h"
+#include "components/image_fetcher/core/image_fetcher.h"
 #include "components/keyed_service/core/keyed_service.h"
 
 class GURL;
 
 namespace base {
 class TaskRunner;
 }
 
+namespace image_fetcher {
+class ImageFetcher;
+}
+
 namespace favicon {
 
 class FaviconService;
 
 // The large icon service provides methods to access large icons. It relies on
 // the favicon service.
 class LargeIconService : public KeyedService {
  public:
   LargeIconService(
       FaviconService* favicon_service,
-      const scoped_refptr<base::TaskRunner>& background_task_runner);
+      const scoped_refptr<base::TaskRunner>& background_task_runner,
+      std::unique_ptr<image_fetcher::ImageFetcher> image_fetcher);
   ~LargeIconService() override;
 
   // Requests the best large icon for the page at |page_url|.
   // Case 1. An icon exists whose size is >= |min_source_size_in_pixel|:
   // - If |desired_size_in_pixel| == 0: returns icon as is.
   // - Else: returns the icon resized to |desired_size_in_pixel|.
   // Case 2. An icon exists whose size is < |min_source_size_in_pixel|:
   // - Extracts dominant color of smaller image, returns a fallback icon style
   //   that has a matching background.
   // Case 3. No icon exists.
   // - Returns the default fallback icon style.
   // For cases 2 and 3, this function returns the style of the fallback icon
   // instead of rendering an icon so clients can render the icon themselves.
   base::CancelableTaskTracker::TaskId GetLargeIconOrFallbackStyle(
     const GURL& page_url,
     int min_source_size_in_pixel,
     int desired_size_in_pixel,
     const favicon_base::LargeIconCallback& callback,
     base::CancelableTaskTracker* tracker);
 
+  // Fetches the best large icon for the page at |page_url| from a Google
+  // favicon server and stores the result in the FaviconService database
+  // (implemented in HistoryService). The write will be a no-op if the local
+  // favicon database contains an icon for |page_url|, so clients are
+  // encouraged to use GetLargeIconOrFallbackStyle() first.
+  //
+  // A minimum size |min_source_size_in_pixel| can be specified as a constraint.
+  //
+  // The callback is triggered when the operation finishes, where |success|
+  // tells whether the fetch actually managed to database a new icon in the
+  // FaviconService.
+  //
+  // WARNING: This function will share the |page_url| with a Google server. This
+  // Can be used only for urls that are not privacy sensitive or for users that
+  // sync their history with Google servers.
+  void GetLargeIconOrFallbackStyleFromGoogleServerSkippingLocalCache(
+      const GURL& page_url,
+      int min_source_size_in_pixel,
+      const base::Callback<void(bool success)>& callback);
+
  private:
   FaviconService* favicon_service_;
   scoped_refptr<base::TaskRunner> background_task_runner_;
 
   // A pre-populated list of icon types to consider when looking for large
   // icons. This is an optimization over populating an icon type vector on each
   // request.
   std::vector<int> large_icon_types_;
 
+  std::unique_ptr<image_fetcher::ImageFetcher> image_fetcher_;
+
   DISALLOW_COPY_AND_ASSIGN(LargeIconService);
 };
 
 }  // namespace favicon
 
 #endif  // COMPONENTS_FAVICON_CORE_LARGE_ICON_SERVICE_H_