Don't swap out the old RenderFrameHost until the new one commits.

content/browser/cross_site_request_manager.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_CROSS_SITE_REQUEST_MANAGER_H_
-#define CONTENT_BROWSER_CROSS_SITE_REQUEST_MANAGER_H_
-
-#include <set>
-#include <utility>
-
-#include "base/basictypes.h"
-#include "base/synchronization/lock.h"
-
-template <typename T> struct DefaultSingletonTraits;
-
-namespace content {
-
-// CrossSiteRequestManager is used to handle bookkeeping for cross-site
-// requests and responses between the UI and IO threads.  Such requests involve
-// a transition from one RenderFrameHost to another within WebContentsImpl, and
-// involve coordination with ResourceDispatcherHost.
-//
-// CrossSiteRequestManager is a singleton that may be used on any thread.
-//
-class CrossSiteRequestManager {
- public:
-  // Returns the singleton instance.
-  static CrossSiteRequestManager* GetInstance();
-
-  // Returns whether the RenderFrameHost specified by the given IDs currently
-  // has a pending cross-site request.  If so, we will have to delay the
-  // response until the previous RenderFrameHost runs its onunload handler.
-  // Called by ResourceDispatcherHost on the IO thread and RenderFrameHost on
-  // the UI thread.
-  bool HasPendingCrossSiteRequest(int renderer_id, int render_frame_id);
-
-  // Sets whether the RenderFrameHost specified by the given IDs currently has a
-  // pending cross-site request.  Called by RenderFrameHost on the UI thread.
-  void SetHasPendingCrossSiteRequest(int renderer_id,
-                                     int render_frame_id,
-                                     bool has_pending);
-
- private:
-  friend struct DefaultSingletonTraits<CrossSiteRequestManager>;
-  typedef std::set<std::pair<int, int> > RenderFrameSet;
-
-  CrossSiteRequestManager();
-  ~CrossSiteRequestManager();
-
-  // You must acquire this lock before reading or writing any members of this
-  // class.  You must not block while holding this lock.
-  base::Lock lock_;
-
-  // Set of (render_process_host_id, render_frame_id) pairs of all
-  // RenderFrameHosts that have pending cross-site requests.  Used to pass
-  // information about the RenderFrameHosts between the UI and IO threads.
-  RenderFrameSet pending_cross_site_frames_;
-
-  DISALLOW_COPY_AND_ASSIGN(CrossSiteRequestManager);
-};
-
-}  // namespace content
-
-#endif  // CONTENT_BROWSER_CROSS_SITE_REQUEST_MANAGER_H_