[gnome-characters/wip/hadess/fix-str-deprecation] Fix deprecation warnings

[Bastien Nocera <hadess src gnome org>]

commit a10d0ef1f72bc4c032d586c00a0c192a7b85b67f
Author: Bastien Nocera <hadess hadess net>
Date:   Fri Jul 26 16:38:42 2019 +0200

    Fix deprecation warnings
    
    Similarly to https://gitlab.gnome.org/GNOME/gnome-characters/issues/44

 src/menu.js   | 4 ++--
 src/window.js | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)
---
diff --git a/src/menu.js b/src/menu.js
index c7510f5..cbd28a4 100644
--- a/src/menu.js
+++ b/src/menu.js
@@ -72,7 +72,7 @@ var MenuPopover = GObject.registerClass({
     _handleSearchChanged(entry) {
         let text = entry.get_text().replace(/^\s+|\s+$/g, '');
         let keywords = text == '' ? [] : text.split(/\s+/);
-        this._keywords = keywords.map(String.toLowerCase);
+        this._keywords = keywords.map(x => x.toLowerCase());
         this._font_listbox.invalidate_filter();
         return true;
     }
@@ -91,7 +91,7 @@ var MenuPopover = GObject.registerClass({
         if (row._family == 'None')
             return true;
 
-        let nameWords = row._family.split(/\s+/).map(String.toLowerCase);
+        let nameWords = row._family.split(/\s+/).map(x => x.toLowerCase());
         return this._keywords.every(function(keyword, index, array) {
             return nameWords.some(function(nameWord, index, array) {
                 return nameWord.indexOf(keyword) >= 0;
diff --git a/src/window.js b/src/window.js
index 1d86cbb..75cc1db 100644
--- a/src/window.js
+++ b/src/window.js
@@ -164,7 +164,7 @@ var MainWindow = GObject.registerClass({
     _handleSearchChanged(entry) {
         const text = entry.get_text().replace(/^\s+|\s+$/g, '');
         let keywords = text == '' ? [] : text.split(/\s+/);
-        keywords = keywords.map(String.toUpperCase);
+        keywords = keywords.map(x => x.toUpperCase());
         if (keywords != this._searchKeywords) {
             this._mainView.cancelSearch();
             this._searchKeywords = keywords;