Prevent creating a swapped out RVH in the same SiteInstance as the current one.

content/browser/frame_host/render_view_host_manager.h

 // 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.
 
 #ifndef CONTENT_BROWSER_FRAME_HOST_RENDER_VIEW_HOST_MANAGER_H_
 #define CONTENT_BROWSER_FRAME_HOST_RENDER_VIEW_HOST_MANAGER_H_
 
 #include "base/basictypes.h"
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 281 matching lines @@
   // cross-site URLs.  Enabled unless we see the --process-per-tab command line
   // switch.  Can be overridden in unit tests.
   bool ShouldTransitionCrossSite();
 
   // Returns true if the two navigation entries are incompatible in some way
   // other than site instances. Cases where this can happen include Web UI
   // to regular web pages. It will cause us to swap RenderViewHosts (and hence
   // RenderProcessHosts) even if the site instance would otherwise be the same.
   // As part of this, we'll also force new SiteInstances and BrowsingInstances.
   // Either of the entries may be NULL.
+  // TODO(creis): Rename to ShouldSwapBrowsingInstancesForNavigation.
   bool ShouldSwapProcessesForNavigation(
       const NavigationEntry* curr_entry,
       const NavigationEntryImpl* new_entry) const;
 
   bool ShouldReuseWebUI(
       const NavigationEntry* curr_entry,
       const NavigationEntryImpl* new_entry) const;
 
   // Returns an appropriate SiteInstance object for the given NavigationEntry,
-  // possibly reusing the current SiteInstance.
-  // Never called if --process-per-tab is used.
+  // possibly reusing the current SiteInstance.  If --process-per-tab is used,
+  // this is only called when ShouldSwapProcessesForNavigation reutrns true.

[ncarter (slow), 2013/11/12 03:38:26]

typo "reutrns"

[Charlie Reis, 2013/11/12 16:09:35]

Done.

   SiteInstance* GetSiteInstanceForEntry(
       const NavigationEntryImpl& entry,
-      SiteInstance* curr_instance);
+      SiteInstance* curr_instance,
+      bool force_browsing_instance_swap);
 
   // Sets up the necessary state for a new RenderViewHost with the given opener.
   bool InitRenderView(RenderViewHost* render_view_host, int opener_route_id);
 
   // Sets the pending RenderViewHost/WebUI to be the active one. Note that this
   // doesn't require the pending render_view_host_ pointer to be non-NULL, since
   // there could be Web UI switching as well. Call this for every commit.
   void CommitPending();
 
   // Shutdown all RenderViewHosts in a SiteInstance. This is called
@@ skipping 62 matching lines @@
   InterstitialPageImpl* interstitial_page_;
 
   NotificationRegistrar registrar_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderViewHostManager);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_FRAME_HOST_RENDER_VIEW_HOST_MANAGER_H_