Purge in-memory localStorage areas if the # of areas exceeds the limit

webkit/dom_storage/dom_storage_namespace.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 WEBKIT_DOM_STORAGE_DOM_STORAGE_NAMESPACE_H_
 #define WEBKIT_DOM_STORAGE_DOM_STORAGE_NAMESPACE_H_
 
 #include <map>
 
 #include "base/basictypes.h"
 #include "base/files/file_path.h"
 #include "base/memory/ref_counted.h"
 #include "webkit/storage/webkit_storage_export.h"
 
 class GURL;
 
 namespace dom_storage {
 
 class DomStorageArea;
 class DomStorageTaskRunner;
 class SessionStorageDatabase;
 
 // Container for the set of per-origin Areas.
 // See class comments for DomStorageContext for a larger overview.
 class WEBKIT_STORAGE_EXPORT DomStorageNamespace
     : public base::RefCountedThreadSafe<DomStorageNamespace> {
  public:
+  // Option for PurgeMemory.
+  enum PurgeOption {
+    // Purge unopened areas only.
+    PURGE_UNOPENED,
+
+    // Purge aggressively, i.e. discard cache even for areas that have
+    // non-zero open count.
+    PURGE_AGGRESSIVE,
+  };
+
   // Constructor for a LocalStorage namespace with id of 0
   // and an optional backing directory on disk.
   DomStorageNamespace(const base::FilePath& directory,  // may be empty
                       DomStorageTaskRunner* task_runner);
 
   // Constructor for a SessionStorage namespace with a non-zero id and an
   // optional backing on disk via |session_storage_database| (may be NULL).
   DomStorageNamespace(int64 namespace_id,
                       const std::string& persistent_namespace_id,
                       SessionStorageDatabase* session_storage_database,
@@ skipping 14 matching lines @@
   DomStorageArea* GetOpenStorageArea(const GURL& origin);
 
   // Creates a clone of |this| namespace including
   // shallow copies of all contained areas.
   // Should only be called for session storage namespaces.
   DomStorageNamespace* Clone(int64 clone_namespace_id,
                              const std::string& clone_persistent_namespace_id);
 
   void DeleteLocalStorageOrigin(const GURL& origin);
   void DeleteSessionStorageOrigin(const GURL& origin);
-  void PurgeMemory();
+  void PurgeMemory(PurgeOption purge);
   void Shutdown();
 
+  unsigned int CountInMemoryAreas() const;
+
  private:
   friend class base::RefCountedThreadSafe<DomStorageNamespace>;
 
   // Struct to hold references to our contained areas and
   // to keep track of how many tabs have a given area open.
   struct AreaHolder {
     scoped_refptr<DomStorageArea> area_;
     int open_count_;
     AreaHolder();
     AreaHolder(DomStorageArea* area, int count);
@@ skipping 11 matching lines @@
   base::FilePath directory_;
   AreaMap areas_;
   scoped_refptr<DomStorageTaskRunner> task_runner_;
   scoped_refptr<SessionStorageDatabase> session_storage_database_;
 };
 
 }  // namespace dom_storage
 
 
 #endif  // WEBKIT_DOM_STORAGE_DOM_STORAGE_NAMESPACE_H_