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..2a33d8328b910d6b3b60cd3a2a4bd7dbac53f204 100644
--- a/content/browser/accessibility/browser_accessibility_com_win.cc
+++ b/content/browser/accessibility/browser_accessibility_com_win.cc
@@ -4094,6 +4094,17 @@ BrowserAccessibilityManager* BrowserAccessibilityComWin::Manager() const {
   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;