Allow AppSearchProvider to provide recommendations.

ui/app_list/search_result.h

Index: ui/app_list/search_result.h
diff --git a/ui/app_list/search_result.h b/ui/app_list/search_result.h
index cf9130c02b86247b0ac967996da4844feea3ac08..d533b7937fa60e176fa5c9e6672b15c93f53e9a4 100644
--- a/ui/app_list/search_result.h
+++ b/ui/app_list/search_result.h
@@ -89,7 +89,7 @@ class APP_LIST_EXPORT SearchResult {
   void set_details_tags(const Tags& tags) { details_tags_ = tags; }
 
   const std::string& id() const { return id_; }
-  double relevance() { return relevance_; }
+  double relevance() const { return relevance_; }
 
   const Actions& actions() const {
     return actions_;