feat(ngAria): Adds button role to ng-click

Closes angular#9254

Author: Marcy Sutton

src/ngAria/aria.js

@@ -20,15 +20,15 @@
  *
  * Below is a more detailed breakdown of the attributes handled by ngAria:
  *
- * | Directive                                   | Supported Attributes                                                                   |
- * |---------------------------------------------|----------------------------------------------------------------------------------------|
- * | {@link ng.directive:ngModel ngModel}        | aria-checked, aria-valuemin, aria-valuemax, aria-valuenow, aria-invalid, aria-required |
- * | {@link ng.directive:ngDisabled ngDisabled}  | aria-disabled                                                                          |
- * | {@link ng.directive:ngShow ngShow}          | aria-hidden                                                                            |
- * | {@link ng.directive:ngHide ngHide}          | aria-hidden                                                                            |
- * | {@link ng.directive:ngClick ngClick}        | tabindex, keypress event                                                               |
- * | {@link ng.directive:ngDblclick ngDblclick}  | tabindex                                                                               |
- * | {@link module:ngMessages ngMessages}        | aria-live                                                                              |
+ * | Directive                                   | Supported Attributes                                                                                |
+ * |---------------------------------------------|-----------------------------------------------------------------------------------------------------|
+ * | {@link ng.directive:ngModel ngModel}        | aria-checked, aria-valuemin, aria-valuemax, aria-valuenow, aria-invalid, aria-required, input roles |
+ * | {@link ng.directive:ngDisabled ngDisabled}  | aria-disabled                                                                                       |
+ * | {@link ng.directive:ngShow ngShow}          | aria-hidden                                                                                         |
+ * | {@link ng.directive:ngHide ngHide}          | aria-hidden                                                                                         |
+ * | {@link ng.directive:ngClick ngClick}        | tabindex, keypress event, button role                                                               |
+ * | {@link ng.directive:ngDblclick ngDblclick}  | tabindex                                                                                            |
+ * | {@link module:ngMessages ngMessages}        | aria-live                                                                                           |
  *
  * Find out more information about each directive by reading the
  * {@link guide/accessibility ngAria Developer Guide}.
@@ -329,6 +329,18 @@ ngAriaModule.directive('ngShow', ['$aria', function($aria) {
           }
         });
       }
+
+      function isNodeOneOf(elem, nodeTypeArray) {
+        for (var i=0; i < nodeTypeArray.length; i++) {
+          if (elem[0].nodeName === nodeTypeArray[i]) {
+            return true;
+          }
+        }
+      }
+
+      if (!elem.attr('role') && !isNodeOneOf(elem, ['BUTTON', 'A'])) {
+        elem.attr('role', 'button');
+      }
     }
   };
 }])