Adding last_forced column to thumbnails database.

chrome/browser/history/history_types.h

Index: chrome/browser/history/history_types.h
diff --git a/chrome/browser/history/history_types.h b/chrome/browser/history/history_types.h
index f23a310aae70dd658dedae4ed527e1efaab12616..a24a79a39122aa121ff98b05cdee90c05e23aee4 100644
--- a/chrome/browser/history/history_types.h
+++ b/chrome/browser/history/history_types.h
@@ -509,11 +509,19 @@ struct KeywordSearchTermRow {
 struct MostVisitedURL {
   MostVisitedURL();
   MostVisitedURL(const GURL& url, const string16& title);
+  MostVisitedURL(const GURL& url,
+                 const string16& title,
+                 const base::Time& last_forced_time);
   ~MostVisitedURL();
 
   GURL url;
   string16 title;
 
+  // If this is a URL for which we want to force a thumbnail, records the last
+  // time it was forced so we can evict it when more recent URLs are requested.
+  // If it's not a forced thumbnail, keep a time of 0.
+  base::Time last_forced_time;
+
   RedirectList redirects;
 
   bool operator==(const MostVisitedURL& other) {