Add heuristics to skip thumbnail generation when it's unnecessary.

chrome/browser/history/top_sites.h

 // Copyright (c) 2010 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_HISTORY_TOP_SITES_H_
 #define CHROME_BROWSER_HISTORY_TOP_SITES_H_
 #pragma once
 
 #include <list>
 #include <set>
@@ skipping 61 matching lines @@
   void GetMostVisitedURLs(CancelableRequestConsumer* consumer,
                           GetTopSitesCallback* callback);
 
   // Get a thumbnail for a given page. Returns true iff we have the thumbnail.
   // This may be invoked on any thread.
   // As this method may be invoked on any thread the ref count needs to be
   // upped before this method returns, so this takes a scoped_refptr*.
   bool GetPageThumbnail(const GURL& url,
                         scoped_refptr<RefCountedBytes>* bytes);
 
+  // Get a thumbnail score for a given page. Returns true iff we have the
+  // thumbnail score.  This may be invoked on any thread. The score will
+  // be copied to |score|.
+  virtual bool GetPageThumbnailScore(const GURL& url, ThumbnailScore* score);
+
   // Invoked from History if migration is needed. If this is invoked it will
   // be before HistoryLoaded is invoked.
   void MigrateFromHistory();
 
   // Invoked with data from migrating thumbnails out of history.
   void FinishHistoryMigration(const ThumbnailMigration& data);
 
   // Invoked from history when it finishes loading. If MigrateFromHistory was
   // not invoked at this point then we load from the top sites service.
   void HistoryLoaded();
@@ skipping 45 matching lines @@
                               const MostVisitedURLList& new_list,
                               TopSitesDelta* delta);
 
   // Query history service for the list of available thumbnails. Returns the
   // handle for the request, or NULL if a request could not be made.
   // Public only for testing purposes.
   CancelableRequestProvider::Handle StartQueryForMostVisited();
 
   bool loaded() const { return loaded_; }
 
+  // Returns true if the given URL is known to the top sites service.
+  virtual bool IsKnownURL(const GURL& url);

[brettw, 2011/01/26 05:55:20]

Both IsKnownURL and IsFull return false if TopSites isn't loaded yet. This is
probably OK for your use in the thumbnail service, but the comments here should
probably note this behavior (the result may be wrong if called "too early").

[satorux1, 2011/01/26 08:14:46]

Good idea. Done.

+
+  // Returns true if the top sites list is full (i.e. we already have the
+  // maximu number of top sites).

[brettw, 2011/01/26 05:55:20]

spelling: maximum

[satorux1, 2011/01/26 08:14:46]

Done.

+  virtual bool IsFull();
+
+ protected:
+  // For allowing inheritance.
+  virtual ~TopSites();
+
  private:
   friend class base::RefCountedThreadSafe<TopSites>;
   friend class TopSitesTest;
 
   typedef std::pair<GURL, Images> TempImage;
   typedef std::list<TempImage> TempImages;
 
   // Enumeration of the possible states history can be in.
   enum HistoryLoadState {
     // We're waiting for history to finish loading.
@@ skipping 13 matching lines @@
 
     // The backend finished loading, but we may need to migrate. This is true if
     // the top sites db didn't exist, or if the db existed but is from an old
     // version.
     TOP_SITES_LOADED_WAITING_FOR_HISTORY,
 
     // Top sites is loaded.
     TOP_SITES_LOADED
   };
 
-  ~TopSites();
-
   // Sets the thumbnail without writing to the database. Useful when
   // reading last known top sites from the DB.
   // Returns true if the thumbnail was set, false if the existing one is better.
   bool SetPageThumbnailNoDB(const GURL& url,
                             const RefCountedBytes* thumbnail_data,
                             const ThumbnailScore& score);
 
   // A version of SetPageThumbnail that takes RefCountedBytes as
   // returned by HistoryService.
   bool SetPageThumbnailEncoded(const GURL& url,
@@ skipping 154 matching lines @@
 
   // Are we loaded?
   bool loaded_;
 
   DISALLOW_COPY_AND_ASSIGN(TopSites);
 };
 
 }  // namespace history
 
 #endif  // CHROME_BROWSER_HISTORY_TOP_SITES_H_