AXMenuListOption should respect role attribute.

third_party/WebKit/LayoutTests/accessibility/role-attribute.html

 <script src="../resources/js-test.js"></script>
 <script src="../resources/accessibility-helper.js"></script>
 <ul role="radiogroup">
     <li role="radio">Explicit Item 1</li>
     <li role="radio">Explicit Item 2</li>
     <li role="radio">Explicit Item 3</li>
 </ul>
 <ol>
     <li>Implicit Item 1</li>
     <li>Implicit Item 2</li>
     <li>Implicit Item 3</li>
 </ol>
 <select multiple role="group">
     <option role="textbox">Explicit Option 1</option>
     <option role="textbox">Explicit Option 2</option>
 </select>
 <select multiple>
     <option>Implicit Option 1</option>
     <option>Implicit Option 2</option>
 </select>
+<select role="group">
+  <option role="textbox">Explicit dropdown 1</option>
+  <option role="textbox">Explicit dropdown 2</option>
+</select>
+<select>
+  <option>Implicit dropdown 1</option>
+  <option>Implicit dropdown 2</option>
+</select>
 <progress value="22" max="100" role="status"></progress>
 <progress value="22" max="100"></progress>
 <input type="range" name="points" min="0" max="10" role="status">
 <input type="range" name="points" min="0" max="10">
 <p>End of test</p>
 <p id="description"></p>
 <div id="console"></div>
 <script>
 description("This tests that the role attribute is not missed.");
 
 if (window.testRunner)
     testRunner.dumpAsText();
 if (window.accessibilityController)
     buildAccessibilityTree(accessibilityController.focusedElement, 0, 1);
 </script>