MD Webui: Improve accessibility of toolbar search field

ui/webui/resources/cr_elements/cr_toolbar/cr_toolbar_search_field.js

Index: ui/webui/resources/cr_elements/cr_toolbar/cr_toolbar_search_field.js
diff --git a/ui/webui/resources/cr_elements/cr_toolbar/cr_toolbar_search_field.js b/ui/webui/resources/cr_elements/cr_toolbar/cr_toolbar_search_field.js
index 6ebc105e84bca5c392fc6f530b257671deaa863d..432c828d6b066bc932034e65f938e7956c98c6b6 100644
--- a/ui/webui/resources/cr_elements/cr_toolbar/cr_toolbar_search_field.js
+++ b/ui/webui/resources/cr_elements/cr_toolbar/cr_toolbar_search_field.js
@@ -81,6 +81,15 @@ Polymer({
   },
 
   /**
+   * @param {boolean} narrow
+   * @return {string}
+   * @private
+   */
+  computeIconAriaHidden_: function(narrow) {
+    return Boolean(!narrow).toString();
+  },
+
+  /**
    * @return {boolean}
    * @private
    */