Convert NavigationMetricsRecorder to use the new navigation callbacks.

content/public/browser/navigation_handle.h

 // Copyright 2015 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_NAVIGATION_HANDLE_H_
 #define CONTENT_PUBLIC_BROWSER_NAVIGATION_HANDLE_H_
 
 #include <memory>
 #include <string>
 
@@ skipping 159 matching lines @@
   // successful commits or error pages that replace the previous page
   // (distinguished by |IsErrorPage|), and false for errors that leave the user
   // on the previous page.
   virtual bool HasCommitted() = 0;
 
   // Whether the navigation resulted in an error page.
   // Note that if an error page reloads, this will return true even though
   // GetNetErrorCode will be net::OK.
   virtual bool IsErrorPage() = 0;
 
+  // The previous main frame URL that the user was on. This may be empty if
+  // there was no last committed entry.
+  virtual const GURL& GetPreviousURL() = 0;
+
   // Returns the remote address of the socket which fetched this resource.
   virtual net::HostPortPair GetSocketAddress() = 0;
 
   // Returns the response headers for the request, or nullptr if there aren't
   // any response headers or they have not been received yet. The response
   // headers may change during the navigation (e.g. after encountering a server
   // redirect). The headers returned should not be modified, as modifications
   // will not be reflected in the network stack.
   virtual const net::HttpResponseHeaders* GetResponseHeaders() = 0;
 
@@ skipping 71 matching lines @@
 
   // The NavigationData that the embedder returned from
   // ResourceDispatcherHostDelegate::GetNavigationData during commit. This will
   // be a clone of the NavigationData.
   virtual NavigationData* GetNavigationData() = 0;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_NAVIGATION_HANDLE_H_