Remove focusFirstElement as it's never called in current Chrome source

ui/webui/resources/js/cr/ui/focus_manager.js

Index: ui/webui/resources/js/cr/ui/focus_manager.js
diff --git a/ui/webui/resources/js/cr/ui/focus_manager.js b/ui/webui/resources/js/cr/ui/focus_manager.js
index c82ec30cc6961a8eaa55ea51e56d75280ab65d9a..d01c72dc2c044e834e5ef9d369a9795bbaa6f647 100644
--- a/ui/webui/resources/js/cr/ui/focus_manager.js
+++ b/ui/webui/resources/js/cr/ui/focus_manager.js
@@ -109,13 +109,6 @@ cr.define('cr.ui', function() {
     },
 
     /**
-     * Attempts to focus the first element in the current dialog.
-     */
-    focusFirstElement: function() {
-      this.focusFirstElement_();
-    },
-
-    /**
      * Selects first appropriate focusable element according to the
      * current focus direction and element type.  If it is a radio button,
      * checked one is selected from the group.