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.
+  // This function also returns false if TopSites isn't loaded yet.
+  virtual bool IsKnownURL(const GURL& url);
+
+  // Returns true if the top sites list is full (i.e. we already have the
+  // maximum number of top sites).  This function also returns false if
+  // TopSites isn't loaded yet.
+  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_