Add TopSites::GetTemporaryThumbnailScore().

chrome/browser/tab_contents/thumbnail_generator.cc

 // Copyright (c) 2011 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.
 
 #include "chrome/browser/tab_contents/thumbnail_generator.h"
 
 #include <algorithm>
 #include <map>
 
 #include "base/memory/scoped_ptr.h"
@@ skipping 653 matching lines @@
                                                const GURL& url) {
   if (!profile || !top_sites)
     return false;
   // Skip if it's in the incognito mode.
   if (profile->IsOffTheRecord())
     return false;
   // Skip if the given URL is not appropriate for history.
   if (!HistoryService::CanAddURL(url))
     return false;
   // Skip if the top sites list is full, and the URL is not known.
-  const bool is_known = top_sites->IsKnownURL(url);
-  if (top_sites->IsFull() && !is_known)
+  if (top_sites->IsFull() && !top_sites->IsKnownURL(url))
     return false;
-  // Skip if we don't have to udpate the existing thumbnail.
+  // Skip if we don't have to udpate the existing thumbnail. Note that an
+  // unknown URL can have a thumbnail score. This can happen if a
+  // thumbnail is set but not yet saved.
   ThumbnailScore current_score;
-  if (is_known &&
-      top_sites->GetPageThumbnailScore(url, &current_score) &&
+  if (top_sites->GetPageThumbnailScore(url, &current_score) &&
       !current_score.ShouldConsiderUpdating())
     return false;
 
   return true;
 }