Persist sessionStorage on disk.

webkit/dom_storage/dom_storage_context.h

Index: webkit/dom_storage/dom_storage_context.h
diff --git a/webkit/dom_storage/dom_storage_context.h b/webkit/dom_storage/dom_storage_context.h
index 5860ec9d87d7624dc53583547740c09ec52c47df..d2b94d48f1b12f2e7bf4dfbff3ef301cf5fc8a24 100644
--- a/webkit/dom_storage/dom_storage_context.h
+++ b/webkit/dom_storage/dom_storage_context.h
@@ -6,6 +6,7 @@
 #define WEBKIT_DOM_STORAGE_DOM_STORAGE_CONTEXT_H_
 
 #include <map>
+#include <set>
 #include <vector>
 
 #include "base/atomic_sequence_num.h"
@@ -34,6 +35,7 @@ class DomStorageArea;
 class DomStorageNamespace;
 class DomStorageSession;
 class DomStorageTaskRunner;
+class SessionStorageDatabase;
 
 // The Context is the root of an object containment hierachy for
 // Namespaces and Areas related to the owning profile.
@@ -159,6 +161,15 @@ class DomStorageContext
   void CloneSessionNamespace(int64 existing_id, int64 new_id,
                              const std::string& new_persistent_id);
 
+  // Starts backing sessionStorage on disk. This function must be called right
+  // after DomStorageContext is created, before it's used.
+  void SetSaveSessionStorageOnDisk();
+
+  // Deletes all namespaces which don't have an associated DomStorageNamespace
+  // alive. This function is used for deleting possible leftover data after an
+  // unclean exit.
+  void StartScavengingUnusedSessionStorage();
+
  private:
   friend class DomStorageContextTest;
   FRIEND_TEST_ALL_PREFIXES(DomStorageContextTest, Basics);
@@ -170,6 +181,14 @@ class DomStorageContext
 
   void ClearSessionOnlyOrigins();
 
+  // For scavenging unused sessionStorages.
+  void FindUnusedNamespaces();
+  void FindUnusedNamespacesInCommitSequence(
+      const std::set<std::string>& namespace_ids_in_use,
+      const std::set<std::string>& protected_persistent_session_ids);
+  void DeleteNextUnusedNamespace();
+  void DeleteNextUnusedNamespaceInCommitSequence();
+
   // Collection of namespaces keyed by id.
   StorageNamespaceMap namespaces_;
 
@@ -194,6 +213,15 @@ class DomStorageContext
   bool is_shutdown_;
   bool force_keep_session_state_;
   scoped_refptr<quota::SpecialStoragePolicy> special_storage_policy_;
+  scoped_refptr<SessionStorageDatabase> session_storage_database_;
+
+  // For cleaning up unused namespaces gradually.
+  bool scavenging_started_;
+  std::vector<std::string> deletable_persistent_namespace_ids_;
+
+  // Persistent namespace IDs to protect from gradual deletion (they will
+  // be needed for session restore).
+  std::set<std::string> protected_persistent_session_ids_;
 };
 
 }  // namespace dom_storage