Implement GetParent, GetChildCount, ChildAtIndex on BrowserAccessibility

content/browser/accessibility/browser_accessibility.cc

Index: content/browser/accessibility/browser_accessibility.cc
diff --git a/content/browser/accessibility/browser_accessibility.cc b/content/browser/accessibility/browser_accessibility.cc
index 95647cb7b211f539967c7e0611bba5342ecc1398..6dc8144dda644347c5cc968eb18bb384fd816f3e 100644
--- a/content/browser/accessibility/browser_accessibility.cc
+++ b/content/browser/accessibility/browser_accessibility.cc
@@ -1149,17 +1149,20 @@ gfx::NativeWindow BrowserAccessibility::GetTopLevelWidget() {
 }
 
 gfx::NativeViewAccessible BrowserAccessibility::GetParent() {
-  NOTREACHED();
+  auto* parent = PlatformGetParent();
+  if (parent && parent->platform_node_)
+    return parent->platform_node_->GetNativeViewAccessible();
   return nullptr;
 }
 
 int BrowserAccessibility::GetChildCount() {
-  NOTREACHED();
-  return -1;
+  return PlatformChildCount();
 }
 
 gfx::NativeViewAccessible BrowserAccessibility::ChildAtIndex(int index) {
-  NOTREACHED();
+  auto* child = PlatformGetChild(index);
+  if (child && child->platform_node_)
+    return child->platform_node_->GetNativeViewAccessible();
   return nullptr;
 }