Send AXLayoutComplete even when document hasn't finished loading yet (reland)

Source/core/accessibility/AXObjectCache.cpp

Index: Source/core/accessibility/AXObjectCache.cpp
diff --git a/Source/core/accessibility/AXObjectCache.cpp b/Source/core/accessibility/AXObjectCache.cpp
index fe407068c151613a9a1877548a25fb5b6719a42e..fa086363c78c845c9123c42ac274ccd862fe5542 100644
--- a/Source/core/accessibility/AXObjectCache.cpp
+++ b/Source/core/accessibility/AXObjectCache.cpp
@@ -804,6 +804,20 @@ void AXObjectCache::handleScrollbarUpdate(ScrollView* view)
     }
 }
 
+void AXObjectCache::handleLayoutComplete(RenderObject* renderer)
+{
+    if (!renderer)
+        return;
+
+    m_computedObjectAttributeCache->clear();
+
+    // Create the AXObject if it didn't yet exist - that's always safe at the end of a layout, and it
+    // allows an AX notification to be sent when a page has its first layout, rather than when the
+    // document first loads.
+    if (AXObject* obj = getOrCreate(renderer))
+        postNotification(obj, obj->document(), AXLayoutComplete, true);
+}
+
 void AXObjectCache::handleAriaExpandedChange(Node* node)
 {
     if (AXObject* obj = getOrCreate(node))