Avoid sending notifications when the bitmap data in history has not changed

chrome/browser/history/thumbnail_database.h

Index: chrome/browser/history/thumbnail_database.h
diff --git a/chrome/browser/history/thumbnail_database.h b/chrome/browser/history/thumbnail_database.h
index dffdc90aad7cd789e842da40283a04e086c689cf..9ee17c798b8ee4a0ede98ddb7fc8205a11eb1ff5 100644
--- a/chrome/browser/history/thumbnail_database.h
+++ b/chrome/browser/history/thumbnail_database.h
@@ -142,6 +142,11 @@ class ThumbnailDatabase {
                         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);
+
   // Deletes the favicon bitmaps for the favicon with with |icon_id|.
   // Returns true if successful.
   bool DeleteFaviconBitmapsForFavicon(FaviconID icon_id);