Add experimental code behind a flag for Content Size Policy

content/content_browser.gypi

 # Copyright (c) 2012 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.
 
 {
   'dependencies': [
     '../base/base.gyp:base_static',
     '../cc/cc.gyp:cc',
     '../cc/cc.gyp:cc_surfaces',
     '../components/components.gyp:display_compositor',
@@ skipping 913 matching lines @@
       'browser/loader/detachable_resource_handler.cc',
       'browser/loader/detachable_resource_handler.h',
       'browser/loader/global_routing_id.h',
       'browser/loader/layered_resource_handler.cc',
       'browser/loader/layered_resource_handler.h',
       'browser/loader/loader_delegate.h',
       'browser/loader/loader_io_thread_notifier.cc',
       'browser/loader/loader_io_thread_notifier.h',
       'browser/loader/mime_type_resource_handler.cc',
       'browser/loader/mime_type_resource_handler.h',
+      'browser/loader/content_size_frame_counter.cc',
+      'browser/loader/content_size_frame_counter.h',
+      'browser/loader/content_size_resource_handler.cc',
+      'browser/loader/content_size_resource_handler.h',
+      'browser/loader/content_size_resource_handler_manager.cc',
+      'browser/loader/content_size_resource_handler_manager.h',
       'browser/loader/navigation_resource_handler.cc',
       'browser/loader/navigation_resource_handler.h',
       'browser/loader/navigation_resource_throttle.cc',
       'browser/loader/navigation_resource_throttle.h',
       'browser/loader/navigation_url_loader.cc',
       'browser/loader/navigation_url_loader.h',
       'browser/loader/navigation_url_loader_delegate.h',
       'browser/loader/navigation_url_loader_factory.h',
       'browser/loader/navigation_url_loader_impl.cc',
       'browser/loader/navigation_url_loader_impl.h',
@@ skipping 1167 matching lines @@
       ],
     }],
     ['OS != "mac" and OS != "android"', {
       'sources!': [
         'browser/gpu/gpu_surface_tracker.cc',
         'browser/gpu/gpu_surface_tracker.h',
       ],
     }],
   ],
 }