WebUI: prevent WebContent to hold an 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 <memory>
+
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "content/public/browser/web_ui_controller.h"
 #include "ui/gfx/native_widget_types.h"
 
 namespace gfx {
 class Size;
 }
 
 namespace content {
 class BrowserContext;
 class WebContents;
 }
 
 namespace ui {
 class WebDialogDelegate;
 }
 
 class ConstrainedWebDialogDelegate {
  public:
   virtual const ui::WebDialogDelegate* GetWebDialogDelegate() const = 0;
   virtual ui::WebDialogDelegate* GetWebDialogDelegate() = 0;
 
   // Called when the dialog is being closed in response to a "dialogClose"
   // message from WebUI.
   virtual void OnDialogCloseFromWebUI() = 0;
 
-  // If called, on dialog closure, the dialog will release its WebContents
-  // instead of destroying it. After which point, the caller will own the
-  // released WebContents.
-  virtual void ReleaseWebContentsOnDialogClose() = 0;
+  // If called, the dialog will release the ownership of its WebContents.
+  // The dialog will continue to use it until it is destroyed.
+  virtual std::unique_ptr<content::WebContents> ReleaseWebContents() = 0;
 
   // Returns the WebContents owned by the constrained window.
   virtual content::WebContents* GetWebContents() = 0;
 
   // Returns the native type used to display the dialog.
   virtual gfx::NativeWindow GetNativeDialog() = 0;
 
   // Returns the minimum size for the dialog.
   virtual gfx::Size GetMinimumSize() const = 0;
 
@@ skipping 18 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_