Reland of Uses the activedescendant_changed event received from Blink to fire the right focus event

content/browser/accessibility/browser_accessibility_manager_win.cc

Index: content/browser/accessibility/browser_accessibility_manager_win.cc
diff --git a/content/browser/accessibility/browser_accessibility_manager_win.cc b/content/browser/accessibility/browser_accessibility_manager_win.cc
index f09eea99cd42b1f9ae3ecdb3b0f1d2dcbe8e5c48..f5bf163e6e2b0a734cf4e7ef0b349c9b170bdae7 100644
--- a/content/browser/accessibility/browser_accessibility_manager_win.cc
+++ b/content/browser/accessibility/browser_accessibility_manager_win.cc
@@ -102,6 +102,11 @@
         IA2_EVENT_DOCUMENT_RELOAD,
         GetRoot()))->Fire();
   }
+}
+
+BrowserAccessibility* BrowserAccessibilityManagerWin::GetFocus() {
+  BrowserAccessibility* focus = BrowserAccessibilityManager::GetFocus();
+  return GetActiveDescendant(focus);
 }
 
 void BrowserAccessibilityManagerWin::NotifyAccessibilityEvent(
@@ -231,6 +236,7 @@
 void BrowserAccessibilityManagerWin::FireFocusEvent(
     BrowserAccessibilityEvent::Source source,
     BrowserAccessibility* node) {
+  DCHECK(node);
   // On Windows, we always fire a FOCUS event on the root of a frame before
   // firing a focus event within that frame.
   if (node->manager() != last_focused_manager_ &&