Handle WebContentsViewMac being destroyed while a <select> menu is showing.

content/browser/browser_plugin/browser_plugin_popup_menu_helper_mac.h

 // Copyright (c) 2012 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.
 
 #ifndef CONTENT_BROWSER_BROWSER_PLUGIN_BROWSER_PLUGIN_POPUP_MENU_HELPER_MAC_H_
 #define CONTENT_BROWSER_BROWSER_PLUGIN_BROWSER_PLUGIN_POPUP_MENU_HELPER_MAC_H_
 
 #include "base/macros.h"
 #include "content/browser/frame_host/popup_menu_helper_mac.h"
 
 namespace content {
 
 class RenderFrameHost;
 class RenderFrameHostImpl;
 
 // This class is similiar to PopupMenuHelperMac but positions the popup relative
 // to the embedder, and issues a reply to the guest.
-class BrowserPluginPopupMenuHelper : public PopupMenuHelper {
+class BrowserPluginPopupMenuHelper : public PopupMenuHelper,
+                                     public PopupMenuHelper::Delegate {
  public:
   // Creates a BrowserPluginPopupMenuHelper that positions popups relative to
   // |embedder_rfh| and will notify |guest_rfh| when a user selects or cancels
   // the popup.
   BrowserPluginPopupMenuHelper(RenderFrameHostImpl* embedder_rfh,
                                RenderFrameHost* guest_rfh);
 
  private:
+  // PopupMenuHelper:
   RenderWidgetHostViewMac* GetRenderWidgetHostView() const override;
 
+  // PopupMenuHelper:Delegate:
+  void OnMenuClosed() override;
+
   RenderFrameHostImpl* embedder_rfh_;
 
   DISALLOW_COPY_AND_ASSIGN(BrowserPluginPopupMenuHelper);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_BROWSER_PLUGIN_BROWSER_PLUGIN_POPUP_MENU_HELPER_MAC_H_