Clean up RenderViewHostManager swapping logic.

content/browser/web_contents/render_view_host_manager.h

Index: content/browser/web_contents/render_view_host_manager.h
diff --git a/content/browser/web_contents/render_view_host_manager.h b/content/browser/web_contents/render_view_host_manager.h
index 68b1704f87faee807dead7f13bacae659cffe145..32d2fca06210fcb8652d4a6e77ddc22f2d0eb09a 100644
--- a/content/browser/web_contents/render_view_host_manager.h
+++ b/content/browser/web_contents/render_view_host_manager.h
@@ -235,26 +235,30 @@ class CONTENT_EXPORT RenderViewHostManager
   // 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.
+  // Returns true if for the navigation from |current_entry| to |new_entry|,
+  // a new SiteInstance and BrowsingInstance should be created (even if we are
+  // in a process model that doesn't usually swap).  This forces a process swap
+  // and severs script connections with existing tabs.  Cases where this can
+  // happen include transitions between WebUI and regular web pages.
   // Either of the entries may be NULL.
-  bool ShouldSwapProcessesForNavigation(
-      const content::NavigationEntry* curr_entry,
+  bool ShouldSwapBrowsingInstanceForNavigation(
+      const content::NavigationEntry* current_entry,
       const content::NavigationEntryImpl* new_entry) const;
 
+  // Returns true if it is safe to reuse the current WebUI when navigating from
+  // |curr_entry| to |new_entry|.
   bool ShouldReuseWebUI(
       const content::NavigationEntry* curr_entry,
       const content::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 ShouldSwapBrowsingInstancesForNavigation returns
+  // true.
   content::SiteInstance* GetSiteInstanceForEntry(
       const content::NavigationEntryImpl& entry,
-      content::SiteInstance* curr_instance);
+      content::SiteInstance* curr_instance,
+      bool force_swap);
 
   // Sets up the necessary state for a new RenderViewHost with the given opener.
   bool InitRenderView(content::RenderViewHost* render_view_host,