Remove the use of ProvisionalChangeToMainFrameUrl from supervised user code.

content/public/browser/web_contents_observer.h

 // 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.
 
 #ifndef CONTENT_PUBLIC_BROWSER_WEB_CONTENTS_OBSERVER_H_
 #define CONTENT_PUBLIC_BROWSER_WEB_CONTENTS_OBSERVER_H_
 
 #include "base/process/kill.h"
 #include "base/process/process_handle.h"
 #include "content/common/content_export.h"
@@ skipping 113 matching lines @@
   // Note that during a cross-process navigation, several provisional loads
   // can be on-going in parallel.
   virtual void DidStartProvisionalLoadForFrame(
       RenderFrameHost* render_frame_host,
       const GURL& validated_url,
       bool is_error_page,
       bool is_iframe_srcdoc) {}
 
   // This method is invoked right after the DidStartProvisionalLoadForFrame if
   // the provisional load affects the main frame, or if the provisional load
-  // was redirected. The latter use case is DEPRECATED. You should listen to
+  // was redirected.
+  //
+  // The latter use case is DEPRECATED. You should listen to
   // WebContentsObserver::DidGetRedirectForResourceRequest instead.
+  //
+  // The former use case is redundant; you should use
+  // DidStartProvisionalLoadForFrame instead, and do a check for the main frame.
+  //
+  // As a result, this whole callback is silly and DEPRECATED. Do not use it.
+  // http://crbug.com/78512
   virtual void ProvisionalChangeToMainFrameUrl(
       const GURL& url,
       RenderFrameHost* render_frame_host) {}
 
   // This method is invoked when the provisional load was successfully
   // committed.
   //
   // If the navigation only changed the reference fragment, or was triggered
   // using the history API (e.g. window.history.replaceState), we will receive
   // this signal without a prior DidStartProvisionalLoadForFrame signal.
@@ skipping 213 matching lines @@
   void ResetWebContents();
 
   WebContentsImpl* web_contents_;
 
   DISALLOW_COPY_AND_ASSIGN(WebContentsObserver);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_WEB_CONTENTS_OBSERVER_H_