Implement BrowserAccessibility accNavigate() in terms of AXPlatformNodeWin.

ui/accessibility/platform/ax_platform_node_win.cc

Index: ui/accessibility/platform/ax_platform_node_win.cc
diff --git a/ui/accessibility/platform/ax_platform_node_win.cc b/ui/accessibility/platform/ax_platform_node_win.cc
index c35356135374000f9e009cf637f1b8c4e12bb47f..9a3619ed7ff31aaba10d3a29579dffd7efb776fc 100644
--- a/ui/accessibility/platform/ax_platform_node_win.cc
+++ b/ui/accessibility/platform/ax_platform_node_win.cc
@@ -280,6 +280,12 @@ STDMETHODIMP AXPlatformNodeWin::accNavigate(
   COM_OBJECT_VALIDATE_VAR_ID_1_ARG(start, end);
   IAccessible* result = nullptr;
 
+  if ((nav_dir == NAVDIR_LASTCHILD || nav_dir == NAVDIR_FIRSTCHILD) &&
+      start.lVal != CHILDID_SELF) {
+    // MSAA states that navigating to first/last child can only be from self.
+    return E_INVALIDARG;
+  }
+
   switch (nav_dir) {
     case NAVDIR_DOWN:
     case NAVDIR_UP: