Don't load subframe history items if a client redirect occurs during load.

content/common/frame_messages.h

 // Copyright 2013 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.
 
 // IPC messages for interacting with frames.
 // Multiply-included message file, hence no include guard.
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 1069 matching lines @@
 IPC_MESSAGE_ROUTED1(FrameHostMsg_UpdateToUniqueOrigin,
                     bool /* is potentially trustworthy unique origin */)
 
 // Sent when the renderer changed the progress of a load.
 IPC_MESSAGE_ROUTED1(FrameHostMsg_DidChangeLoadProgress,
                     double /* load_progress */)
 
 // Requests that the given URL be opened in the specified manner.
 IPC_MESSAGE_ROUTED1(FrameHostMsg_OpenURL, FrameHostMsg_OpenURL_Params)
 
+// If a cross-process navigation was started for the initial history load in
+// this subframe, this tries to cancel it to allow a client redirect to happen
+// instead.
+IPC_MESSAGE_ROUTED0(FrameHostMsg_CancelInitialHistoryLoad)
+
 // Notifies the browser that a frame finished loading.
 IPC_MESSAGE_ROUTED1(FrameHostMsg_DidFinishLoad,
                     GURL /* validated_url */)
 
 // Initiates a download based on user actions like 'ALT+click'.
 IPC_MESSAGE_CONTROL5(FrameHostMsg_DownloadUrl,
                      int /* render_view_id */,
                      int /* render_frame_id */,
                      GURL /* url */,
                      content::Referrer /* referrer */,
@@ skipping 464 matching lines @@
 // nearest find result in the sending frame.
 IPC_MESSAGE_ROUTED2(FrameHostMsg_GetNearestFindResult_Reply,
                     int /* nfr_request_id */,
                     float /* distance */)
 #endif
 
 // Adding a new message? Stick to the sort order above: first platform
 // independent FrameMsg, then ifdefs for platform specific FrameMsg, then
 // platform independent FrameHostMsg, then ifdefs for platform specific
 // FrameHostMsg.