Update the accessibility tree when a modal dialog is opened/closed.

Source/core/accessibility/AXObject.cpp

Index: Source/core/accessibility/AXObject.cpp
diff --git a/Source/core/accessibility/AXObject.cpp b/Source/core/accessibility/AXObject.cpp
index 1c247f6cb0658f79118d2aba496946f222f02182..0e5217e13569a5bf98765e7e2d155c280a4fd2b2 100644
--- a/Source/core/accessibility/AXObject.cpp
+++ b/Source/core/accessibility/AXObject.cpp
@@ -289,14 +289,15 @@ AXObjectInclusion AXObject::defaultObjectInclusion() const
 
 bool AXObject::isInertOrAriaHidden() const
 {
-    if (equalIgnoringCase(getAttribute(aria_hiddenAttr), "true"))
-        return true;
-    if (node() && node()->isInert())
-        return true;
-
-    for (AXObject* object = parentObject(); object; object = object->parentObject()) {
+    bool mightBeInInertSubtree = true;
+    for (const AXObject* object = this; object; object = object->parentObject()) {
         if (equalIgnoringCase(object->getAttribute(aria_hiddenAttr), "true"))
             return true;
+        if (mightBeInInertSubtree && object->node()) {
+            if (object->node()->isInert())
+                return true;
+            mightBeInInertSubtree = false;
+        }
     }
 
     return false;