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

content/public/browser/web_contents_observer.h

Index: content/public/browser/web_contents_observer.h
diff --git a/content/public/browser/web_contents_observer.h b/content/public/browser/web_contents_observer.h
index af9593ec9baccb8aaece98a4605247b3ee6cbb90..131e0d85b1ac054c67987109a03759a11ba98cf6 100644
--- a/content/public/browser/web_contents_observer.h
+++ b/content/public/browser/web_contents_observer.h
@@ -129,22 +129,6 @@ class CONTENT_EXPORT WebContentsObserver : public IPC::Listener,
       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
-  // 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.
   //