[wip] Introduce SiteInstanceKeepAlive.

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 SiteInstanceKeepAlive;
 
 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 const GURL& GetSiteURL() const OVERRIDE;
   virtual SiteInstance* GetRelatedSiteInstance(const GURL& url) OVERRIDE;
   virtual bool IsRelatedSiteInstance(const SiteInstance* instance) OVERRIDE;
   virtual BrowserContext* GetBrowserContext() const OVERRIDE;
 
+  scoped_ptr<SiteInstanceKeepAlive> AcquireKeepAlive();
+
   // 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
   // avoid dedicating an unused SiteInstance to it (e.g., in a new tab).
@@ skipping 78 matching lines @@
 
   // The web site that this SiteInstance is rendering pages for.
   GURL site_;
 
   // Whether SetSite has been called.
   bool has_site_;
 
   DISALLOW_COPY_AND_ASSIGN(SiteInstanceImpl);
 };
 
+class CONTENT_EXPORT SiteInstanceKeepAlive {
+ public:
+  explicit SiteInstanceKeepAlive(scoped_refptr<SiteInstanceImpl> instance);

[mfomitchev, 2014/02/14 16:21:36]

Perhaps we should make this constructor non-puiblic and force clients to use
AcquireKeepAlive() instead?

+  ~SiteInstanceKeepAlive();
+
+ private:
+  scoped_refptr<SiteInstanceImpl> instance_;
+
+  DISALLOW_COPY_AND_ASSIGN(SiteInstanceKeepAlive);
+};
+
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_SITE_INSTANCE_IMPL_H_