Add handling to respect role attribute in AXObjects.

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>
+<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>