[Thumbnails DB] Allow setting last_requested time when accessing favicons.

components/history/core/browser/thumbnail_database.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 COMPONENTS_HISTORY_CORE_BROWSER_THUMBNAIL_DATABASE_H_
 #define COMPONENTS_HISTORY_CORE_BROWSER_THUMBNAIL_DATABASE_H_
 
 #include <vector>
 
 #include "base/gtest_prod_util.h"
@@ skipping 83 matching lines @@
   // The |time| indicates the access time, and is used to detect when the
   // favicon should be refreshed.
   // |pixel_size| is the pixel dimensions of |icon_data|.
   // Returns the id of the added bitmap or 0 if unsuccessful.
   FaviconBitmapID AddFaviconBitmap(
       favicon_base::FaviconID icon_id,
       const scoped_refptr<base::RefCountedMemory>& icon_data,
       base::Time time,
       const gfx::Size& pixel_size);
 
+  // The same as AddFaviconBitmap(), it also marks the bitmap as "on-demand".
+  //
+  // On-demand bitmaps are those that are fetched without visiting their page.
+  // For this reason, their life-time cannot be bound to the life-time of the
+  // corresponding visit in history.
+  // - These bitmaps are evicted from the database based on the last time they
+  //   get requested. The last requested time is initially set to |time| and is
+  //   further updated by calling KeepOnDemandFavicon().
+  // - Furthermore, on-demand bitmaps are immediately marked as expired. Hence,
+  //   they are always replaced by standard favicons whenever their page gets
+  //   visited.
+  FaviconBitmapID AddOnDemandFaviconBitmap(
+      favicon_base::FaviconID icon_id,
+      const scoped_refptr<base::RefCountedMemory>& icon_data,
+      base::Time time,
+      const gfx::Size& pixel_size);
+
   // Sets the bitmap data and the last updated time for the favicon bitmap at
   // |bitmap_id|.
   // Returns true if successful.
   bool SetFaviconBitmap(FaviconBitmapID bitmap_id,
                         scoped_refptr<base::RefCountedMemory> bitmap_data,
                         base::Time time);
 
   // Sets the last updated time for the favicon bitmap at |bitmap_id|.
   // Returns true if successful.
   bool SetFaviconBitmapLastUpdateTime(FaviconBitmapID bitmap_id,
                                       base::Time time);
 
-  // Sets the last requested time for the favicon bitmap at |bitmap_id|.
-  // Returns true if successful.
-  bool SetFaviconBitmapLastRequestedTime(FaviconBitmapID bitmap_id,
-                                         base::Time time);
-
   // Deletes the favicon bitmap with |bitmap_id|.
   // Returns true if successful.
   bool DeleteFaviconBitmap(FaviconBitmapID bitmap_id);
 
   // Favicons ------------------------------------------------------------------
 
   // Sets the the favicon as out of date. This will set |last_updated| for all
   // of the bitmaps for |icon_id| to be out of date.
   bool SetFaviconOutOfDate(favicon_base::FaviconID icon_id);
 
+  // Mark all on-demand bitmaps at |icon_url| as requested at |time|. This
+  // postpones their automatic eviction from the database. Not all calls end up
+  // in a write into the DB:
+  // - it is no-op if the bitmaps are not stored using SetOnDemandFaviconBitmap;
+  // - the updates of the last requested time have limited frequency for each
+  //   particular bitmap (e.g. once per week). This limits the overhead of
+  //   cache management for on-demand favicons.
+  // Returns true if successful.
+  bool TouchOnDemandFavicon(const GURL& icon_url, base::Time time);
+
   // Returns the id of the entry in the favicon database with the specified url
   // and icon type.
   // Returns 0 if no entry exists for the specified url.
   favicon_base::FaviconID GetFaviconIDForFaviconURL(
       const GURL& icon_url,
       favicon_base::IconType icon_type);
 
   // Gets the icon_url, icon_type and sizes for the specified |icon_id|.
   bool GetFaviconHeader(favicon_base::FaviconID icon_id,
                         GURL* icon_url,
@@ skipping 122 matching lines @@
 
   sql::Connection db_;
   sql::MetaTable meta_table_;
 
   HistoryBackendClient* backend_client_;
 };
 
 }  // namespace history
 
 #endif  // COMPONENTS_HISTORY_CORE_BROWSER_THUMBNAIL_DATABASE_H_