Use BrowserAccessibilityComWin::Destroy to clear delegate and owner.

content/browser/accessibility/browser_accessibility_com_win.h

Index: content/browser/accessibility/browser_accessibility_com_win.h
diff --git a/content/browser/accessibility/browser_accessibility_com_win.h b/content/browser/accessibility/browser_accessibility_com_win.h
index ef16af35e9a667b84fdcb85de72e1af73f46c449..ffdcd4b34361b057de56bb6a95384db725ceafdd 100644
--- a/content/browser/accessibility/browser_accessibility_com_win.h
+++ b/content/browser/accessibility/browser_accessibility_com_win.h
@@ -745,6 +745,13 @@ class __declspec(uuid("562072fe-3390-43b1-9e2c-dd4118f5ac79"))
   BrowserAccessibilityWin* GetOwner() const { return owner_; }
   void SetOwner(BrowserAccessibilityWin* owner) { owner_ = owner; }
 
+  // Called when BrowserAccessibilityWin is about to go away.
+  // At this point, we detach from it.
+  void detach() {

[dmazzoni, 2017/05/10 06:15:50]

I think this is the same as AXPlatformNode::Destroy(), can't you override that?

I'm fine with renaming it Detach() or Release()

+    owner_ = nullptr;
+    delegate_ = nullptr;
+  }
+
   BrowserAccessibilityManager* owners_manager() const;
 
   // Returns the IA2 text attributes for this object.