Call RemoveObserver from OnWidgetDestroying

ui/views/accessibility/native_view_accessibility.cc

 // Copyright (c) 2013 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 "ui/views/accessibility/native_view_accessibility.h"
 
 #include "base/strings/utf_string_conversions.h"
 #include "ui/accessibility/ax_view_state.h"
 #include "ui/events/event_utils.h"
 #include "ui/views/controls/native/native_view_host.h"
@@ skipping 185 matching lines @@
   ui::AXViewState state;
   view_->GetAccessibleState(&state);
   if (state.set_value_callback.is_null())
     return false;
 
   state.set_value_callback.Run(new_value);
   return true;
 }
 
 void NativeViewAccessibility::OnWidgetDestroying(Widget* widget) {
-  if (parent_widget_ == widget)
+  if (parent_widget_ == widget) {
+    parent_widget_->RemoveObserver(this);
     parent_widget_ = nullptr;
+  }
 }
 
 void NativeViewAccessibility::SetParentWidget(Widget* parent_widget) {
   if (parent_widget_)
     parent_widget_->RemoveObserver(this);
   parent_widget_ = parent_widget;
   parent_widget_->AddObserver(this);
 }
 
 void NativeViewAccessibility::PopulateChildWidgetVector(
@@ skipping 25 matching lines @@
               child_widget_platform_node->GetDelegate());
       if (child_widget_view_accessibility->parent_widget() != widget)
         child_widget_view_accessibility->SetParentWidget(widget);
     }
 
     result_child_widgets->push_back(child_widget);
   }
 }
 
 }  // namespace views