Add experimental code behind a flag for Content Size Policy

content/browser/loader/DEPS

 # The core loading code in this directory is being transitioned into a separate
 # Mojo networking service. See http://crbug.com/598073. The first stage is to
 # decouple the code that will be moved from the rest of content. These rules
 # help ensure that we don't add more includes, and can progressively reduce the
 # code's dependencies.
 #
 # For each file, the first section shows includes that are allowed (i.e. because
 # they are for files that will be moving as well). The second section, separated
 # by a comment, lists files that we will have to decouple.
 specific_include_rules = {
@@ skipping 112 matching lines @@
     "+content/browser/bad_message.h",
     "+content/browser/blob_storage/chrome_blob_storage_context.h",
     "+content/browser/child_process_security_policy_impl.h",
     "+content/browser/download/download_resource_handler.h",
     "+content/browser/download/save_file_manager.h",
     "+content/browser/download/save_file_resource_handler.h",
     "+content/browser/download/save_types.h",
     "+content/browser/frame_host/frame_tree.h",
     "+content/browser/frame_host/navigation_request_info.h",
     "+content/browser/frame_host/navigator.h",
+    "+content/browser/loader/content_size_resource_handler_manager.h",
     "+content/browser/loader/cross_site_resource_handler.h",
     "+content/browser/loader/detachable_resource_handler.h",
     "+content/browser/loader/mime_type_resource_handler.h",
     "+content/browser/loader/navigation_resource_handler.h",
     "+content/browser/loader/navigation_resource_throttle.h",
     "+content/browser/loader/navigation_url_loader_impl_core.h",
     "+content/browser/loader/redirect_to_file_resource_handler.h",
     "+content/browser/loader/upload_data_stream_builder.h",
     "+content/browser/resource_context_impl.h",
     "+content/browser/service_worker/foreign_fetch_request_handler.h",
@@ skipping 118 matching lines @@
     "+content/browser/loader/sync_resource_handler.h",
     "+content/public/browser/resource_dispatcher_host_delegate.h",
     "+content/public/browser/resource_request_info.h",
     "+content/public/common/resource_response.h",
 
 
     # TODO: To be replaced by mojo.
     "+content/common/resource_messages.h",
   ],
 }