Remove WebContentsObserver::ProvisionalChangeToMainFrameUrl and all the code supporting it.

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 "content/common/content_export.h"
 #include "content/common/content_param_traits.h"
 #include "content/common/frame_message_enums.h"
@@ skipping 499 matching lines @@
 // elements which can be animated by the navigation destination to provide
 // a transition effect during load.
 IPC_MESSAGE_ROUTED2(FrameHostMsg_DidStartProvisionalLoadForFrame,
                     GURL /* url */,
                     bool /* is_transition_navigation */)
 
 // Sent when the renderer fails a provisional load with an error.
 IPC_MESSAGE_ROUTED1(FrameHostMsg_DidFailProvisionalLoadWithError,
                     FrameHostMsg_DidFailProvisionalLoadWithError_Params)
 
-// Sent when a provisional load on the main frame redirects.
-IPC_MESSAGE_ROUTED3(FrameHostMsg_DidRedirectProvisionalLoad,
-                    int /* page_id */,
-                    GURL /* source_url*/,
-                    GURL /* target_url */)
-
 // Notifies the browser that a frame in the view has changed. This message
 // has a lot of parameters and is packed/unpacked by functions defined in
 // render_messages.h.
 IPC_MESSAGE_ROUTED1(FrameHostMsg_DidCommitProvisionalLoad,
                     FrameHostMsg_DidCommitProvisionalLoad_Params)
 
 // Notifies the browser that a document has been loaded.
 IPC_MESSAGE_ROUTED0(FrameHostMsg_DidFinishDocumentLoad)
 
 IPC_MESSAGE_ROUTED3(FrameHostMsg_DidFailLoadWithError,
@@ skipping 219 matching lines @@
 IPC_MESSAGE_ROUTED0(FrameHostMsg_DidFirstVisuallyNonEmptyPaint)
 
 #if defined(OS_MACOSX) || defined(OS_ANDROID)
 
 // Message to show/hide a popup menu using native controls.
 IPC_MESSAGE_ROUTED1(FrameHostMsg_ShowPopup,
                     FrameHostMsg_ShowPopup_Params)
 IPC_MESSAGE_ROUTED0(FrameHostMsg_HidePopup)
 
 #endif