[Favicon] Add new fallback icon rendering flow.

chrome/browser/favicon/favicon_service.h

 // Copyright (c) 2012 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_FAVICON_FAVICON_SERVICE_H_
 #define CHROME_BROWSER_FAVICON_FAVICON_SERVICE_H_
 
+#include <memory>
 #include <vector>
 
 #include "base/callback.h"
 #include "base/containers/hash_tables.h"
 #include "base/memory/ref_counted.h"
 #include "base/task/cancelable_task_tracker.h"
 #include "components/favicon_base/favicon_callback.h"
 #include "components/favicon_base/favicon_types.h"
 #include "components/keyed_service/core/keyed_service.h"
 
 class FaviconClient;
 class GURL;
 class HistoryService;
 struct ImportedFaviconUsage;
 class Profile;
 
+namespace favicon_base {
+class FallbackIconService;
+struct FallbackIconSpecs;
+}  // namespace favicon_base
+
 // The favicon service provides methods to access favicons. It calls the history
 // backend behind the scenes. The callbacks are run asynchronously, even in the
 // case of an error.
 class FaviconService : public KeyedService {
  public:
   // TODO(jif): Remove usage of Profile. http://crbug.com/378208.
   // The FaviconClient must outlive the constructed FaviconService.
   FaviconService(Profile* profile, FaviconClient* favicon_client);
 
   ~FaviconService() override;
@@ skipping 38 matching lines @@
   // result for each of the resource scale factors. There are less entries if a
   // single/ result is the best bitmap to use for several resource scale
   // factors.
   base::CancelableTaskTracker::TaskId GetFavicon(
       const GURL& icon_url,
       favicon_base::IconType icon_type,
       int desired_size_in_dip,
       const favicon_base::FaviconResultsCallback& callback,
       base::CancelableTaskTracker* tracker);
 
+  // Generates a fallback favicon for |icon_url| with size |size_in_pixel|,
+  // using auxiliary rendering parameters in |params|. |size_in_pixel| = 0
+  // specifies maximum fallback favicon size. |specs| does not need to live
+  // beyond the function call.

[pkotwicz, 2015/01/19 04:32:02]

My hope is that this function will never be needed. Ideally, the only way to get
a fallback icon would be by requesting a normal favicon for icon URL if:
- a favicon for |icon_url| was not stored at the desired size in the favicon
database.

For now FallbackFaviconSource (not FaviconSource) can call directly into
FallbackIconService

[huangs, 2015/01/20 22:20:41]

Simplified, and named everything "FallbackIcon" or "fallback-icon".

+  base::CancelableTaskTracker::TaskId GetRawFallbackFaviconImage(
+      const GURL& icon_url,
+      favicon_base::IconType icon_type,
+      int desired_size_in_pixel,
+      const favicon_base::FallbackIconSpecs& specs,
+      const favicon_base::FaviconRawBitmapCallback& callback,
+      base::CancelableTaskTracker* tracker);
+
   //////////////////////////////////////////////////////////////////////////////
   // Methods to request favicon bitmaps from the history backend for |page_url|.
   // |page_url| is the web page the favicon is associated with.
   // (e.g. <http://www.google.com>)
 
   // Requests the favicon for the page at |page_url| of type
   // favicon_base::FAVICON and of size gfx::kFaviconSize. The returned
   // gfx::Image is populated with representations for all of the scale factors
   // supported by the platform (e.g. MacOS). If data is unavailable for some or
   // all of the scale factors, the bitmaps with the best matching sizes are
@@ skipping 115 matching lines @@
 
   // Avoid repeated requests to download missing favicon.
   void UnableToDownloadFavicon(const GURL& icon_url);
   bool WasUnableToDownloadFavicon(const GURL& icon_url) const;
   void ClearUnableToDownloadFavicons();
 
  private:
   typedef uint32 MissingFaviconURLHash;
   base::hash_set<MissingFaviconURLHash> missing_favicon_urls_;
   HistoryService* history_service_;
+  std::unique_ptr<favicon_base::FallbackIconService> fallback_icon_service_;
   Profile* profile_;
   FaviconClient* favicon_client_;
 
   // Helper function for GetFaviconImageForPageURL(), GetRawFaviconForPageURL()
   // and GetFaviconForPageURL().
   base::CancelableTaskTracker::TaskId GetFaviconForPageURLImpl(
       const GURL& page_url,
       int icon_types,
       const std::vector<int>& desired_sizes_in_pixel,
       const favicon_base::FaviconResultsCallback& callback,
@@ skipping 16 matching lines @@
   void RunFaviconRawBitmapCallbackWithBitmapResults(
       const favicon_base::FaviconRawBitmapCallback& callback,
       int desired_size_in_pixel,
       const std::vector<favicon_base::FaviconRawBitmapResult>&
           favicon_bitmap_results);
 
   DISALLOW_COPY_AND_ASSIGN(FaviconService);
 };
 
 #endif  // CHROME_BROWSER_FAVICON_FAVICON_SERVICE_H_