Change net::LOAD_MAIN_FRAME to net::LOAD_MAIN_FRAME_DEPRECATED to discourage

net/base/load_flags_list.h

 // Copyright (c) 2011 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.
 
 // This is the list of load flags and their values. For the enum values,
 // include the file "net/base/load_flags.h".
 //
 // Here we define the values using a macro LOAD_FLAG, so it can be
 // expanded differently in some places (for example, to automatically
 // map a load flag value to its symbolic name).
@@ skipping 36 matching lines @@
 // This load will not send any cookies.
 LOAD_FLAG(DO_NOT_SEND_COOKIES, 1 << 9)
 
 // This load will not send authentication data (user name/password)
 // to the server (as opposed to the proxy).
 LOAD_FLAG(DO_NOT_SEND_AUTH_DATA, 1 << 10)
 
 // This should only be used for testing (set by HttpNetworkTransaction).
 LOAD_FLAG(IGNORE_ALL_CERT_ERRORS, 1 << 11)
 
+// DO NOT USE THIS FLAG
+// The network stack should not have frame level knowledge.  Any pre-connect
+// or pre-resolution requiring that knowledge should be done from the
+// stack embedder.
 // Indicate that this is a top level frame, so that we don't assume it is a
 // subresource and speculatively pre-connect or pre-resolve when a referring
 // page is loaded.
-LOAD_FLAG(MAIN_FRAME, 1 << 12)
+LOAD_FLAG(MAIN_FRAME_DEPRECATED, 1 << 12)
 
 // Indicates that this load was motivated by the rel=prefetch feature,
 // and is (in theory) not intended for the current frame.
 LOAD_FLAG(PREFETCH, 1 << 13)
 
 // Indicates that this load could cause deadlock if it has to wait for another
 // request. Overrides socket limits. Must always be used with MAXIMUM_PRIORITY.
 LOAD_FLAG(IGNORE_LIMITS, 1 << 14)
 
 // Indicates that the operation is somewhat likely to be due to an
 // explicit user action. This can be used as a hint to treat the
 // request with higher priority.
 LOAD_FLAG(MAYBE_USER_GESTURE, 1 << 15)
 
 // Indicates that the username:password portion of the URL should not
 // be honored, but that other forms of authority may be used.
 LOAD_FLAG(DO_NOT_USE_EMBEDDED_IDENTITY, 1 << 16)
 
 // The creator of this URLRequest wishes to receive stale responses when allowed
 // by the "Cache-Control: stale-while-revalidate" directive and is able to issue
 // an async revalidation to update the cache.
 LOAD_FLAG(SUPPORT_ASYNC_REVALIDATION, 1 << 17)
 
 // Indicates that this request is not to be migrated to a new network when QUIC
 // connection migration is enabled.
 LOAD_FLAG(DISABLE_CONNECTION_MIGRATION, 1 << 18)