accessibility: Simpler AXTree root accessor.

content/test/accessibility_browser_test_utils.cc

Index: content/test/accessibility_browser_test_utils.cc
diff --git a/content/test/accessibility_browser_test_utils.cc b/content/test/accessibility_browser_test_utils.cc
index a2f381559764f3c5947822eb01b090e7af8e657c..94245ecb7fb20a2881c708e0ba9070e91e488f07 100644
--- a/content/test/accessibility_browser_test_utils.cc
+++ b/content/test/accessibility_browser_test_utils.cc
@@ -92,7 +92,7 @@ bool AccessibilityNotificationWaiter::IsAboutBlank() {
   // Skip any accessibility notifications related to "about:blank",
   // to avoid a possible race condition between the test beginning
   // listening for accessibility events and "about:blank" loading.
-  const ui::AXNodeData& root = GetAXTree().GetRoot()->data();
+  const ui::AXNodeData& root = GetAXTree().root()->data();
   for (size_t i = 0; i < root.string_attributes.size(); ++i) {
     if (root.string_attributes[i].first != ui::AX_ATTR_DOC_URL)
       continue;