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
  TestSafeBrowsingBlockingPage(SafeBrowsingService* service,
                               TabContents* tab_contents,
                               const UnsafeResourceList& unsafe_resources)
      : SafeBrowsingBlockingPage(service, tab_contents, unsafe_resources) {
    malware_details_proceed_delay_ms_ = 100;
    wait_for_delete_ = false;
  }

  TestSafeBrowsingBlockingPage(SafeBrowsingService* service,
                               TabContents* tab_contents,
                               const UnsafeResourceList& unsafe_resources)
      : SafeBrowsingBlockingPage(service, tab_contents, unsafe_resources) {
    malware_details_proceed_delay_ms_ = 100;
    wait_for_delete_ = false;
  }
