Don't delete the current NavigationEntry when leaving an interstitial page.

BUG=107182
TEST=See bug

Review URL: http://codereview.chromium.org/8976014

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@115189 0039d316-1c4b-4281-b951-d872f2087c98
  virtual void OnBlockingPageComplete(bool proceed) {
    if (proceed)
      user_response_ = OK;
    else
      user_response_ = CANCEL;
  }

  virtual void OnBlockingPageComplete(bool proceed) {
    if (proceed)
      user_response_ = OK;
    else
      user_response_ = CANCEL;
  }
