PlzNavigate: add cancel navigation logic for uncommitted requests

content/browser/frame_host/navigation_request.h

 // Copyright 2014 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_BROWSER_FRAME_HOST_NAVIGATION_REQUEST_H_
 #define CONTENT_BROWSER_FRAME_HOST_NAVIGATION_REQUEST_H_
 
 #include "base/basictypes.h"
 #include "base/memory/ref_counted.h"
 #include "content/browser/frame_host/navigation_request_info.h"
@@ skipping 13 matching lines @@
   ~NavigationRequest();
 
   const NavigationRequestInfo& info_for_testing() const { return info_; }
   int64 frame_node_id() const { return frame_node_id_; }
 
   // Called on the UI thread by the RenderFrameHostManager which owns the
   // NavigationRequest. After calling this function, |body| can no longer be
   // manipulated on the UI thread.
   void BeginNavigation(scoped_refptr<ResourceRequestBody> body);
 
+  int64 navigation_request_id() const { return navigation_request_id_; }
+
  private:
+  // The next available browser-global navigation request ID.
+  static int64 next_navigation_request_id_;
+
+  const int64 navigation_request_id_;
   const NavigationRequestInfo info_;
   const int64 frame_node_id_;
 
   DISALLOW_COPY_AND_ASSIGN(NavigationRequest);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_FRAME_HOST_NAVIGATION_REQUEST_H_