Add a check that the planned replacement for page id for updating the history offset works.

content/renderer/render_frame_impl.cc

 // 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.
 
 #include "content/renderer/render_frame_impl.h"
 
 #include <map>
 #include <string>
 
 #include "base/auto_reset.h"
@@ skipping 2672 matching lines @@
         !navigation_state->start_params().should_replace_current_entry) {
       // Advance our offset in session history, applying the length limit.
       // There is now no forward history.
       render_view_->history_list_offset_++;
       if (render_view_->history_list_offset_ >= kMaxSessionHistoryEntries)
         render_view_->history_list_offset_ = kMaxSessionHistoryEntries - 1;
       render_view_->history_list_length_ =
           render_view_->history_list_offset_ + 1;
     }
   } else {
-    if (navigation_state->request_params().page_id != -1) {
+    const RequestNavigationParams& request_params =
+        navigation_state->request_params();
+    if (request_params.page_id != -1) {
       // This is a successful session history navigation!
-      render_view_->page_id_ = navigation_state->request_params().page_id;
+      render_view_->page_id_ = request_params.page_id;
 
       render_view_->history_list_offset_ =
-          navigation_state->request_params().pending_history_list_offset;
+          request_params.pending_history_list_offset;
     }
+    // Page id is going away (http://crbug.com/369661); ensure that a
+    // replacement that doesn't use page id is equivalent in all cases.
+    CHECK_EQ(request_params.page_id != -1,
+             request_params.nav_entry_id != 0 &&
+             !request_params.intended_as_new_entry);
   }
 
   bool sent = Send(
       new FrameHostMsg_DidAssignPageId(routing_id_, render_view_->page_id_));
   CHECK(sent);  // http://crbug.com/407376
 
   FOR_EACH_OBSERVER(RenderViewObserver, render_view_->observers_,
                     DidCommitProvisionalLoad(frame, is_new_navigation));
   FOR_EACH_OBSERVER(
       RenderFrameObserver, observers_,
@@ skipping 2224 matching lines @@
 #elif defined(ENABLE_BROWSER_CDMS)
         cdm_manager_,
 #endif
         this);
   }
 
   return cdm_factory_;
 }
 
 }  // namespace content