Use BrowserAccessibilityComWin::Destroy to clear delegate and owner.

content/browser/accessibility/browser_accessibility_com_win.cc

Index: content/browser/accessibility/browser_accessibility_com_win.cc
diff --git a/content/browser/accessibility/browser_accessibility_com_win.cc b/content/browser/accessibility/browser_accessibility_com_win.cc
index 09ee21849deb157a18f4dc48e2021eacf5493449..61cd3a7b8cd2484f31fc9c5a587663ab249bb79e 100644
--- a/content/browser/accessibility/browser_accessibility_com_win.cc
+++ b/content/browser/accessibility/browser_accessibility_com_win.cc
@@ -4094,6 +4094,15 @@ BrowserAccessibilityManager* BrowserAccessibilityComWin::Manager() const {
   return manager;
 }
 
+//
+// AXPlatformNode overrides
+//
+void BrowserAccessibilityComWin::Destroy() {
+  // Detach BrowserAccessibilityWin from us.
+  owner_ = nullptr;
+  AXPlatformNodeWin::Destroy();
+}
+
 std::vector<base::string16> BrowserAccessibilityComWin::ComputeTextAttributes()
     const {
   std::vector<base::string16> attributes;