AX: Incomplete object information with focus event on dynamic created div

Implementation bases on PR from: WebKit/WebKit#25479

When the element is dynamically created and focused, the focus change event should be
deferred in case renderer is not available yet but document needs style recalculation.

Author: pgorszkowski-igalia

Source/WebCore/accessibility/AXObjectCache.cpp

@@ -1364,14 +1364,34 @@ void AXObjectCache::handleRowCountChanged(AXCoreObject* axObject, Document* docu
     postNotification(axObject, document, AXRowCountChanged);
 }
 
-void AXObjectCache::deferFocusedUIElementChangeIfNeeded(Node* oldNode, Node* newNode)
+static bool shouldDeferFocusChange(Element* element)
 {
-    if (nodeAndRendererAreValid(newNode) && rendererNeedsDeferredUpdate(*newNode->renderer())) {
-        m_deferredFocusedNodeChange.append({ oldNode, newNode });
-        if (!newNode->renderer()->needsLayout() && !m_performCacheUpdateTimer.isActive())
+    if (!element)
+        return false;
+
+    auto* renderer = element->renderer();
+    if (renderer && rendererNeedsDeferredUpdate(*renderer))
+        return true;
+
+    // We also want to defer handling focus changes for nodes that haven't yet attached their renderer.
+    if (const auto* style = element->existingComputedStyle())
+        return !renderer && element->rendererIsNeeded(*style);
+    // No existing style, so we can't easily determine whether this element will need a renderer.
+    // Resolving style is expensive and we don't want to do it now, so make this decision assuming
+    // a renderer just hasn't been attached yet, indicated by it being nullptr.
+    return !renderer;
+}
+
+void AXObjectCache::deferFocusedUIElementChangeIfNeeded(Element* oldElement, Element* newElement)
+{
+    if (shouldDeferFocusChange(newElement)) {
+        m_deferredFocusedNodeChange.append({ oldElement, newElement });
+       // Don't start the timer if a layout is pending, as the layout will trigger a cache update.
+        bool needsLayout = newElement->renderer() && newElement->renderer()->needsLayout();
+        if (!needsLayout && !m_performCacheUpdateTimer.isActive())
             m_performCacheUpdateTimer.startOneShot(0_s);
     } else
-        handleFocusedUIElementChanged(oldNode, newNode);
+        handleFocusedUIElementChanged(oldElement, newElement);
 }
 
 void AXObjectCache::deferMenuListValueChange(Element* element)

Source/WebCore/accessibility/AXObjectCache.h

@@ -199,7 +199,7 @@ class AXObjectCache {
     void loadingFinished() { updateLoadingProgress(1); }
     double loadingProgress() const { return m_loadingProgress; }
 
-    void deferFocusedUIElementChangeIfNeeded(Node* oldFocusedNode, Node* newFocusedNode);
+    void deferFocusedUIElementChangeIfNeeded(Element* oldElement, Element* newElement);
     void deferModalChange(Element*);
     void deferMenuListValueChange(Element*);
     void deferNodeAddedOrRemoved(Node*);
@@ -647,7 +647,7 @@ inline void AXObjectCache::childrenChanged(Node*, Node*) { }
 inline void AXObjectCache::childrenChanged(RenderObject*, RenderObject*) { }
 inline void AXObjectCache::childrenChanged(AccessibilityObject*) { }
 inline void AXObjectCache::valueChanged(Element*) { }
-inline void AXObjectCache::deferFocusedUIElementChangeIfNeeded(Node*, Node*) { }
+inline void AXObjectCache::deferFocusedUIElementChangeIfNeeded(Element*, Element*) { }
 inline void AXObjectCache::deferRecomputeIsIgnoredIfNeeded(Element*) { }
 inline void AXObjectCache::deferRecomputeIsIgnored(Element*) { }
 inline void AXObjectCache::deferTextChangedIfNeeded(Node*) { }