Add experimental code behind a flag for Content Size Policy

content/browser/frame_host/navigation_handle_impl.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/browser/frame_host/navigation_handle_impl.h"
 
 #include <utility>
 
 #include "base/logging.h"
 #include "content/browser/devtools/render_frame_devtools_agent_host.h"
 #include "content/browser/frame_host/frame_tree_node.h"
 #include "content/browser/frame_host/navigator.h"
 #include "content/browser/frame_host/navigator_delegate.h"
+#include "content/browser/loader/loader_io_thread_notifier.h"
 #include "content/browser/service_worker/service_worker_context_wrapper.h"
 #include "content/common/frame_messages.h"
 #include "content/common/resource_request_body_impl.h"
 #include "content/public/browser/content_browser_client.h"
 #include "content/public/common/browser_side_navigation_policy.h"
 #include "content/public/common/content_client.h"
 #include "net/url_request/redirect_info.h"
 #include "url/gurl.h"
 #include "url/url_constants.h"
 
@@ skipping 530 matching lines @@
       GetContentClient()->browser()->CreateThrottlesForNavigation(this);
   if (throttles_to_register.size() > 0) {
     throttles_.insert(throttles_.end(), throttles_to_register.begin(),
                       throttles_to_register.end());
     throttles_to_register.weak_clear();
   }
   std::unique_ptr<NavigationThrottle> devtools_throttle =
       RenderFrameDevToolsAgentHost::CreateThrottleForNavigation(this);
   if (devtools_throttle)
     throttles_.push_back(devtools_throttle.release());
+
+  NavigationThrottle* content_size_throttle =
+      LoaderIOThreadNotifier::MaybeCreateThrottle(this);
+  if (content_size_throttle)
+    throttles_.push_back(base::WrapUnique(content_size_throttle));
 }
 
 }  // namespace content