1 files changed, 136 insertions, 0 deletions
diff --git a/chrome/browser/browsing_instance.h b/chrome/browser/browsing_instance.h
new file mode 100644
index 0000000..e44f747
--- /dev/null
+++ b/chrome/browser/browsing_instance.h
@@ -0,0 +1,136 @@
+// Copyright (c) 2010 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 CHROME_BROWSER_BROWSING_INSTANCE_H_
+#define CHROME_BROWSER_BROWSING_INSTANCE_H_
+
+#include "base/hash_tables.h"
+#include "base/logging.h"
+#include "base/ref_counted.h"
+#include "chrome/browser/profile.h"
+
+class GURL;
+class SiteInstance;
+
+///////////////////////////////////////////////////////////////////////////////
+//
+// BrowsingInstance class
+//
+// A browsing instance corresponds to the notion of a "unit of related browsing
+// contexts" in the HTML 5 spec.  Intuitively, it represents a collection of
+// tabs and frames that can have script connections to each other.  In that
+// sense, it reflects the user interface, and not the contents of the tabs and
+// frames.
+//
+// We further subdivide a BrowsingInstance into SiteInstances, which represent
+// the documents within each BrowsingInstance that are from the same site and
+// thus can have script access to each other.  Different SiteInstances can
+// safely run in different processes, because their documents cannot access
+// each other's contents (due to the same origin policy).
+//
+// It is important to only have one SiteInstance per site within a given
+// BrowsingInstance.  This is because any two documents from the same site
+// might be able to script each other if they are in the same BrowsingInstance.
+// Thus, they must be rendered in the same process.
+//
+// If the process-per-site model is in use, then we ensure that there is only
+// one SiteInstance per site for the entire profile, not just for each
+// BrowsingInstance.  This reduces the number of renderer processes we create.
+// (This is currently only true if --process-per-site is specified at the
+// command line.)
+//
+// A BrowsingInstance is live as long as any SiteInstance has a reference to
+// it.  A SiteInstance is live as long as any NavigationEntry or RenderViewHost
+// have references to it.  Because both classes are RefCounted, they do not
+// need to be manually deleted.
+//
+// Currently, the BrowsingInstance class is not visible outside of the
+// SiteInstance class.  To get a new SiteInstance that is part of the same
+// BrowsingInstance, use SiteInstance::GetRelatedSiteInstance.  Because of
+// this, BrowsingInstances and SiteInstances are tested together in
+// site_instance_unittest.cc.
+//
+///////////////////////////////////////////////////////////////////////////////
+class BrowsingInstance : public base::RefCounted<BrowsingInstance> {
+ public:
+  // Create a new BrowsingInstance.
+  explicit BrowsingInstance(Profile* profile)
+      : profile_(profile) {
+  }
+
+  // Returns whether the process-per-site model is in use (globally or just for
+  // the given url), in which case we should ensure there is only one
+  // SiteInstance per site for the entire profile, not just for this
+  // BrowsingInstance.
+  virtual bool ShouldUseProcessPerSite(const GURL& url);
+
+  // Get the profile to which this BrowsingInstance belongs.
+  Profile* profile() { return profile_; }
+
+  // Returns whether this BrowsingInstance has registered a SiteInstance for
+  // the site of the given URL.
+  bool HasSiteInstance(const GURL& url);
+
+  // Get the SiteInstance responsible for rendering the given URL.  Should
+  // create a new one if necessary, but should not create more than one
+  // SiteInstance per site.
+  SiteInstance* GetSiteInstanceForURL(const GURL& url);
+
+  // Adds the given SiteInstance to our map, to ensure that we do not create
+  // another SiteInstance for the same site.
+  void RegisterSiteInstance(SiteInstance* site_instance);
+
+  // Removes the given SiteInstance from our map, after all references to it
+  // have been deleted.  This means it is safe to create a new SiteInstance
+  // if the user later visits a page from this site, within this
+  // BrowsingInstance.
+  void UnregisterSiteInstance(SiteInstance* site_instance);
+
+ protected:
+  friend class base::RefCounted<BrowsingInstance>;
+
+  // Virtual to allow tests to extend it.
+  virtual ~BrowsingInstance() {
+    // We should only be deleted when all of the SiteInstances that refer to
+    // us are gone.
+    DCHECK(site_instance_map_.empty());
+  }
+
+ private:
+  // Map of site to SiteInstance, to ensure we only have one SiteInstance per
+  // site.  The site string should be the possibly_invalid_spec() of a GURL
+  // obtained with SiteInstance::GetSiteForURL.
+  typedef base::hash_map<std::string, SiteInstance*> SiteInstanceMap;
+
+  // Map of Profile runtime Id to SiteInstanceMap, for use in the
+  // process-per-site model.
+  typedef base::hash_map<ProfileId, SiteInstanceMap> ProfileSiteInstanceMap;
+
+  // Returns a pointer to the relevant SiteInstanceMap for this object.  If the
+  // process-per-site model is in use, or if process-per-site-instance is in
+  // use and |url| matches a site for which we always use one process (e.g.,
+  // the new tab page), then this returns the SiteInstanceMap for the entire
+  // profile.  If not, this returns the BrowsingInstance's own private
+  // SiteInstanceMap.
+  SiteInstanceMap* GetSiteInstanceMap(Profile* profile, const GURL& url);
+
+  // Common profile to which all SiteInstances in this BrowsingInstance
+  // must belong.
+  Profile* const profile_;
+
+  // Map of site to SiteInstance, to ensure we only have one SiteInstance per
+  // site.  The site string should be the possibly_invalid_spec() of a GURL
+  // obtained with SiteInstance::GetSiteForURL.  Note that this map may not
+  // contain every active SiteInstance, because a race exists where two
+  // SiteInstances can be assigned to the same site.  This is ok in rare cases.
+  // This field is only used if we are not using process-per-site.
+  SiteInstanceMap site_instance_map_;
+
+  // Global map of Profile to SiteInstanceMap, for process-per-site.
+  static ProfileSiteInstanceMap profile_site_instance_map_;
+
+  DISALLOW_COPY_AND_ASSIGN(BrowsingInstance);
+};
+
+#endif  // CHROME_BROWSER_BROWSING_INSTANCE_H_