Ensure forced process swaps use the correct page_id and SiteInstance.

content/browser/tab_contents/render_view_host_manager.cc

 // Copyright (c) 2011 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/browser/tab_contents/render_view_host_manager.h"
 
 #include "base/command_line.h"
 #include "base/logging.h"
 #include "content/browser/renderer_host/render_view_host.h"
 #include "content/browser/renderer_host/render_view_host_delegate.h"
@@ skipping 373 matching lines @@
   // NOTE: This is only called when ShouldTransitionCrossSite is true.
 
   const GURL& dest_url = entry.url();
   NavigationController& controller = delegate_->GetControllerForRenderManager();
   content::BrowserContext* browser_context = controller.browser_context();
 
   // If the entry has an instance already we should use it, unless the URL
   // is part of an app that has been installed or uninstalled since the last
   // visit.
   if (entry.site_instance()) {
-    if (entry.site_instance()->HasWrongProcessForURL(dest_url))
-      return curr_instance->GetRelatedSiteInstance(dest_url);
-    else
-      return entry.site_instance();
+    if (entry.site_instance()->HasWrongProcessForURL(dest_url)) {
+      // If we need to swap to a different SiteInstance, the new one should have
+      // the same max_page_id as the current one so that it identifies new vs
+      // existing navigations correctly.  We also need to update the entry's
+      // SiteInstance, which we will do in TabContents::NavigateToEntry.
+      SiteInstance* new_instance =
+          curr_instance->GetRelatedSiteInstance(dest_url);
+      new_instance->UpdateMaxPageID(curr_instance->max_page_id());
+      return new_instance;
+    }
+    return entry.site_instance();
   }
 
   // (UGLY) HEURISTIC, process-per-site only:
   //
   // If this navigation is generated, then it probably corresponds to a search
   // query.  Given that search results typically lead to users navigating to
   // other sites, we don't really want to use the search engine hostname to
   // determine the site instance for this navigation.
   //
   // NOTE: This can be removed once we have a way to transition between
@@ skipping 394 matching lines @@
   }
 }
 
 bool RenderViewHostManager::IsSwappedOut(RenderViewHost* rvh) {
   if (!rvh->site_instance())
     return false;
 
   return swapped_out_hosts_.find(rvh->site_instance()->id()) !=
       swapped_out_hosts_.end();
 }