Check BrowsingInstance before swapping prerenders.

content/browser/site_instance_impl.h

 // Copyright (c) 2012 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_SITE_INSTANCE_IMPL_H_
 #define CONTENT_BROWSER_SITE_INSTANCE_IMPL_H_
 
 #include "content/browser/renderer_host/render_process_host_impl.h"
 #include "content/common/content_export.h"
 #include "content/public/browser/render_process_host_observer.h"
 #include "content/public/browser/site_instance.h"
 #include "url/gurl.h"
 
 namespace content {
 class RenderProcessHostFactory;
 
 class CONTENT_EXPORT SiteInstanceImpl : public SiteInstance,
                                         public RenderProcessHostObserver {
  public:
   // SiteInstance interface overrides.
   virtual int32 GetId() OVERRIDE;
   virtual bool HasProcess() const OVERRIDE;
   virtual RenderProcessHost* GetProcess() OVERRIDE;
+  virtual BrowserContext* GetBrowserContext() const OVERRIDE;
   virtual const GURL& GetSiteURL() const OVERRIDE;
   virtual SiteInstance* GetRelatedSiteInstance(const GURL& url) OVERRIDE;
   virtual bool IsRelatedSiteInstance(const SiteInstance* instance) OVERRIDE;
-  virtual BrowserContext* GetBrowserContext() const OVERRIDE;
+  virtual size_t GetRelatedActiveContentsCount() const OVERRIDE;
 
   // Set the web site that this SiteInstance is rendering pages for.
   // This includes the scheme and registered domain, but not the port.  If the
   // URL does not have a valid registered domain, then the full hostname is
   // stored.
   void SetSite(const GURL& url);
   bool HasSite() const;
 
   // Returns whether there is currently a related SiteInstance (registered with
   // BrowsingInstance) for the site of the given url.  If so, we should try to
@@ skipping 12 matching lines @@
 
   // Decrease the number of active views in this SiteInstance. This is
   // decreased when a view is destroyed, or a currently active view is
   // swapped out.
   void decrement_active_view_count() { active_view_count_--; }
 
   // Get the number of active views which belong to this
   // SiteInstance. If there is no active view left in this
   // SiteInstance, all view in this SiteInstance can be safely
   // discarded to save memory.
   size_t active_view_count() { return active_view_count_; }

[davidben, 2014/04/29 17:01:25]

Oh, I mentioned this out-of-band, but the reason this value doesn't work is
because it also counts pending RVHs. The existing use of that count (when
swapped out RVHs can go away) should including pending RVHs because there may be
a race.

[Charlie Reis, 2014/04/29 17:31:08]

This count is also specific to the SiteInstance and not the BrowsingInstance,
right?  I agree that it wouldn't work.

[davidben, 2014/04/29 21:31:40]

Yeah. Though if that were the only issue, BrowsingInstance could maintain a set
of all SiteInstances attached to it and sum over the active_view_counts.

 
+  void IncrementRelatedActiveContentsCount();

[Charlie Reis, 2014/04/29 17:31:08]

These need comments explaining that they're for tracking the number of
WebContents in the BrowsingInstance, not counting pending hosts.

[davidben, 2014/04/29 21:31:40]

Done.

+  void DecrementRelatedActiveContentsCount();
+
   // Sets the global factory used to create new RenderProcessHosts.  It may be
   // NULL, in which case the default BrowserRenderProcessHost will be created
   // (this is the behavior if you don't call this function).  The factory must
   // be set back to NULL before it's destroyed; ownership is not transferred.
   static void set_render_process_host_factory(
       const RenderProcessHostFactory* rph_factory);
 
   // Get the effective URL for the given actual URL.  This allows the
   // ContentBrowserClient to override the SiteInstance's site for certain URLs.
   // For example, Chrome uses this to replace hosted app URLs with extension
@@ skipping 48 matching lines @@
 
   // Whether SetSite has been called.
   bool has_site_;
 
   DISALLOW_COPY_AND_ASSIGN(SiteInstanceImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_SITE_INSTANCE_IMPL_H_