Use BrowserAccessibilityComWin::Destroy to clear delegate and owner.

content/browser/accessibility/browser_accessibility_com_win.cc

 // Copyright (c) 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/accessibility/browser_accessibility_com_win.h"
 
 #include <UIAutomationClient.h>
 #include <UIAutomationCoreApi.h>
 
 #include <algorithm>
@@ skipping 4076 matching lines @@
 
 BrowserAccessibilityManager* BrowserAccessibilityComWin::Manager() const {
   auto* owner = GetOwner();
   DCHECK(owner);
 
   auto* manager = owner->manager();
   DCHECK(manager);
   return manager;
 }
 
+//
+// AXPlatformNode overrides
+//
+void BrowserAccessibilityComWin::Destroy() {
+  // Detach BrowserAccessibilityWin from us.
+  owner_ = nullptr;
+  delegate_ = nullptr;
+
+  AXPlatformNode::Destroy();

[dmazzoni, 2017/05/10 15:17:52]

You definitely want AXPlatformNodeWin::Destroy() here otherwise you're
shadowing useful behvarior.

Do you need to clear delegate_? I think the superclass should do that.
Maybe DCHECK(!delegate_) instead.

+}
+
 std::vector<base::string16> BrowserAccessibilityComWin::ComputeTextAttributes()
     const {
   std::vector<base::string16> attributes;
 
   // We include list markers for now, but there might be other objects that are
   // auto generated.
   // TODO(nektar): Compute what objects are auto-generated in Blink.
   if (GetOwner()->GetRole() == ui::AX_ROLE_LIST_MARKER)
     attributes.push_back(L"auto-generated:true");
   else
@@ skipping 1618 matching lines @@
 
 BrowserAccessibilityComWin* ToBrowserAccessibilityComWin(
     BrowserAccessibility* obj) {
   if (!obj || !obj->IsNative())
     return nullptr;
   auto* result = static_cast<BrowserAccessibilityWin*>(obj)->GetCOM();
   return result;
 }
 
 }  // namespace content