Bug 1354211 - Add element.isReadOnly. r=automatedtester

Introduces new function for testing whether an element is read-only.
This content IDL attribute only applies to <input> and <textarea>
elements.

MozReview-Commit-ID: 1YLizKUYMU6

--HG--
extra : rebase_source : 2d7dcd34d20cf0dd2f0e0087b28e5eeebfa72fad

testing/marionette/element.js

@@ -782,6 +782,22 @@ element.isSelected = function(el) {
   return false;
 };
 
+/**
+ * An element is considered read only if it is an
+ * <code>&lt;input&gt;</code> or <code>&lt;textarea&gt;</code>
+ * element whose <code>readOnly</code> content IDL attribute is set.
+ *
+ * @param {Element} el
+ *     Element to test is read only.
+ *
+ * @return {boolean}
+ *     True if element is read only.
+ */
+element.isReadOnly = function(el) {
+  return element.isDOMElement(el) &&
+      ["input", "textarea"].includes(el.localName) && el.readOnly;
+};
+
 /**
  * This function generates a pair of coordinates relative to the viewport
  * given a target element and coordinates relative to that element's

testing/marionette/test_element.js

@@ -194,6 +194,16 @@ add_test(function test_isDOMWindow() {
   run_next_test();
 });
 
+add_test(function test_isReadOnly() {
+  ok(!element.isReadOnly(null));
+  ok(!element.isReadOnly(domEl));
+  ok(!element.isReadOnly(new DOMElement("p", {readOnly: true})));
+  ok(element.isReadOnly(new DOMElement("input", {readOnly: true})));
+  ok(element.isReadOnly(new DOMElement("textarea", {readOnly: true})));
+
+  run_next_test();
+});
+
 add_test(function test_coordinates() {
   let p = element.coordinates(domEl);
   ok(p.hasOwnProperty("x"));