Provide assumed favicon for intents if service provider page was never visited.

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 138c308af2a79acb3675ada0d6d4c794c80c1a1d..f554267f9643cf3fbc4a535afa41ecb87253b601 100644
--- a/chrome/browser/history/thumbnail_database.h
+++ b/chrome/browser/history/thumbnail_database.h
@@ -165,6 +165,10 @@ class ThumbnailDatabase {
   // Checks whether a favicon is used by any URLs in the database.
   bool HasMappingFor(FaviconID id);
 
+  // Clones the existing mappings from |old_page_url| if |new_page_url| has no
+  // mappings. Otherwise, will leave mappings alone.
+  bool CloneIconMapping(const GURL& old_page_url, const GURL& new_page_url);
+
   // Temporary IconMapping -----------------------------------------------------
   //
   // Creates a temporary table to store icon mapping. Icon mapping will be