Only call TextChanged on existing AXObjects. This avoids triggering the code which calls UpdateDist…

third_party/WebKit/LayoutTests/accessibility/presentation-owned-elements.html

 <script src="../resources/js-test.js"></script>
 <script src="../resources/accessibility-helper.js"></script>
 <div>These lists have a static text role because they have a presentation role.</div>
 <ul role="presentation">
     <li>Presentation Item 1</li>
     <li>Presentation Item 2</li>
 </ul>
 
 <div>The first list item has a listitem role even if ul has a presentation role because it has an explicit role.</div>
 <ul role="presentation">
@@ skipping 60 matching lines @@
 </div>
 
 <p>End of test</p>
 <p id="description"></p>
 <div id="console"></div>
 <script>
 description("This test make sure that presentation role is inherited to required owned elements.");
 
 if (window.testRunner)
     testRunner.dumpAsText();
+
 if (window.accessibilityController) {
+    // Ensure we've seen all nodes in accessibility tree.
+    traverseAccessibilityTree(accessibilityController.rootElement);
     buildAccessibilityTree(accessibilityController.focusedElement, 0, 1);
 }
 </script>