Purge browser cache for dom storage in a smarter way

content/browser/dom_storage/dom_storage_namespace.h

 // Copyright 2013 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_DOM_STORAGE_DOM_STORAGE_NAMESPACE_H_
 #define CONTENT_BROWSER_DOM_STORAGE_DOM_STORAGE_NAMESPACE_H_
 
 #include <stdint.h>
 
 #include <map>
@@ skipping 16 matching lines @@
 class DOMStorageTaskRunner;
 class SessionStorageDatabase;
 
 // Container for the set of per-origin Areas.
 // See class comments for DOMStorageContextImpl for a larger overview.
 class CONTENT_EXPORT DOMStorageNamespace
     : public base::RefCountedThreadSafe<DOMStorageNamespace> {
  public:
   // Option for PurgeMemory.
   enum PurgeOption {
+    // Determines is purging is required based on the usage and the platform.
+    PURGE_IF_NEEDED,
+
     // 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.
@@ skipping 26 matching lines @@
   // Should only be called for session storage namespaces.
   DOMStorageNamespace* Clone(int64_t clone_namespace_id,
                              const std::string& clone_persistent_namespace_id);
 
   void DeleteLocalStorageOrigin(const GURL& origin);
   void DeleteSessionStorageOrigin(const GURL& origin);
   void PurgeMemory(PurgeOption purge);
   void Shutdown();
   void Flush();
 
-  unsigned int CountInMemoryAreas() const;
-
   // Adds memory statistics to |pmd| for chrome://tracing.
   void OnMemoryDump(base::trace_event::ProcessMemoryDump* pmd);
 
   void GetOriginsWithAreas(std::vector<GURL>* origins) 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);
     AreaHolder(const AreaHolder& other);
     ~AreaHolder();
   };
   typedef std::map<GURL, AreaHolder> AreaMap;
 
   ~DOMStorageNamespace();
 
   // Returns a pointer to the area holder in our map or NULL.
   AreaHolder* GetAreaHolder(const GURL& origin);
 
+  // Helper to determine is purging is needed based on the usage and the
+  // platform.
+  bool ShouldPurgeMemory();
+
   int64_t namespace_id_;
   std::string persistent_namespace_id_;
   base::FilePath directory_;
   AreaMap areas_;
   scoped_refptr<DOMStorageTaskRunner> task_runner_;
   scoped_refptr<SessionStorageDatabase> session_storage_database_;
+  bool is_low_end_device_;
 };
 
 }  // namespace content
 
 
 #endif  // CONTENT_BROWSER_DOM_STORAGE_DOM_STORAGE_NAMESPACE_H_