Add a readonly attribute to cr-input.

ui/webui/resources/cr_elements/cr_input/cr_input.js

Index: ui/webui/resources/cr_elements/cr_input/cr_input.js
diff --git a/ui/webui/resources/cr_elements/cr_input/cr_input.js b/ui/webui/resources/cr_elements/cr_input/cr_input.js
index 3f8f253c8911a6213888389484f703aff9b39ef8..4258ecd6985cdbec6b7bd4706ecc40e94c50f081 100644
--- a/ui/webui/resources/cr_elements/cr_input/cr_input.js
+++ b/ui/webui/resources/cr_elements/cr_input/cr_input.js
@@ -46,6 +46,15 @@ Polymer('cr-input', {
     disabled: {value: false, reflect: true},
 
     /**
+     * Set to true to make the input read-only.
+     *
+     * @attribute readonly
+     * @type boolean
+     * @default false
+     */
+    readonly: {value: false, reflect: true},
+
+    /**
      * Set to true to mark the input as required.
      *
      * @attribute required