Delete unneeded pending entries in DidFailProvisionalLoad to prevent a spoof.

BUG=280512
BUG=278899
TEST=See bug for repro steps.

Review URL: https://chromiumcodereview.appspot.com/23978003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@222146 0039d316-1c4b-4281-b951-d872f2087c98
  void WaitUntilScreenshotIsReady() {
    if (!encoding_screenshot_in_progress_)
      return;
    message_loop_runner_ = new content::MessageLoopRunner;
    message_loop_runner_->Run();
  }

  void WaitUntilScreenshotIsReady() {
    if (!encoding_screenshot_in_progress_)
      return;
    message_loop_runner_ = new content::MessageLoopRunner;
    message_loop_runner_->Run();
  }
