Revert of Add a NavigationThrottle to the public content/ interface

content/public/browser/navigation_throttle.cc

-// Copyright 2015 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.
-
-#include "content/public/browser/navigation_throttle.h"
-
-namespace content {
-
-NavigationThrottle::NavigationThrottle(NavigationHandle* navigation_handle)
-    : navigation_handle_(navigation_handle) {}
-
-NavigationThrottle::~NavigationThrottle() {}
-
-NavigationThrottle::ThrottleCheckResult NavigationThrottle::WillStartRequest() {
-  return NavigationThrottle::PROCEED;
-}
-
-NavigationThrottle::ThrottleCheckResult
-NavigationThrottle::WillRedirectRequest() {
-  return NavigationThrottle::PROCEED;
-}
-
-}  // namespace content