WebUI: prevent WebContent to hold invalid pointer.

chrome/browser/ui/webui/constrained_web_dialog_ui.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 CHROME_BROWSER_UI_WEBUI_CONSTRAINED_WEB_DIALOG_UI_H_
 #define CHROME_BROWSER_UI_WEBUI_CONSTRAINED_WEB_DIALOG_UI_H_
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "content/public/browser/web_ui_controller.h"
@@ skipping 56 matching lines @@
  public:
   explicit ConstrainedWebDialogUI(content::WebUI* web_ui);
   ~ConstrainedWebDialogUI() override;
 
   // WebUIController implementation:
   void RenderFrameCreated(content::RenderFrameHost* render_frame_host) override;
 
   // Sets the delegate on the WebContents.
   static void SetConstrainedDelegate(content::WebContents* web_contents,
                                      ConstrainedWebDialogDelegate* delegate);
+  static void ClearConstrainedDelegate(content::WebContents* web_contents);
 
  protected:
   // Returns the ConstrainedWebDialogDelegate saved with the WebContents.
   // Returns NULL if no such delegate is set.
   ConstrainedWebDialogDelegate* GetConstrainedDelegate();
 
  private:
   // JS Message Handler
   void OnDialogCloseMessage(const base::ListValue* args);
 
@@ skipping 21 matching lines @@
 // |min_size| is the minimum size of the dialog.
 // |max_size| is the maximum size of the dialog.
 ConstrainedWebDialogDelegate* ShowConstrainedWebDialogWithAutoResize(
     content::BrowserContext* browser_context,
     ui::WebDialogDelegate* delegate,
     content::WebContents* overshadowed,
     const gfx::Size& min_size,
     const gfx::Size& max_size);
 
 #endif  // CHROME_BROWSER_UI_WEBUI_CONSTRAINED_WEB_DIALOG_UI_H_