Purge browser cache for dom storage in a smarter way

content/browser/dom_storage/dom_storage_context_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_DOM_STORAGE_DOM_STORAGE_CONTEXT_IMPL_H_
 #define CONTENT_BROWSER_DOM_STORAGE_DOM_STORAGE_CONTEXT_IMPL_H_
 
 #include <stdint.h>
 
 #include <map>
@@ skipping 47 matching lines @@
 // all contained Areas, the shallow copies refer to the same refcounted Map,
 // and does a deep copy-on-write if needed.
 //
 // Classes intended to be used by an embedder are DOMStorageContextImpl,
 // DOMStorageHost, and DOMStorageSession. The other classes are for
 // internal consumption.
 class CONTENT_EXPORT DOMStorageContextImpl
     : public base::RefCountedThreadSafe<DOMStorageContextImpl>,
       public base::trace_event::MemoryDumpProvider {
  public:
+  typedef std::map<int64_t, scoped_refptr<DOMStorageNamespace>>
+      StorageNamespaceMap;
+
   // An interface for observing Local and Session Storage events on the
   // background thread.
   class EventObserver {
    public:
     // |old_value| may be null on initial insert.
     virtual void OnDOMStorageItemSet(
         const DOMStorageArea* area,
         const base::string16& key,
         const base::string16& new_value,
         const base::NullableString16& old_value,
         const GURL& page_url) = 0;
     virtual void OnDOMStorageItemRemoved(
         const DOMStorageArea* area,
         const base::string16& key,
         const base::string16& old_value,
         const GURL& page_url) = 0;
     virtual void OnDOMStorageAreaCleared(
         const DOMStorageArea* area,
         const GURL& page_url) = 0;
 
    protected:
     virtual ~EventObserver() {}
   };
 
+  // Option for PurgeMemory.
+  enum PurgeOption {
+    // Determines if 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,
+  };
+
   // |localstorage_directory| and |sessionstorage_directory| may be empty
   // for incognito browser contexts.
   DOMStorageContextImpl(const base::FilePath& localstorage_directory,
                         const base::FilePath& sessionstorage_directory,
                         storage::SpecialStoragePolicy* special_storage_policy,
                         DOMStorageTaskRunner* task_runner);
 
   // Returns the directory path for localStorage, or an empty directory, if
   // there is no backing on disk.
   const base::FilePath& localstorage_directory() {
@@ skipping 66 matching lines @@
 
   // Starts backing sessionStorage on disk. This function must be called right
   // after DOMStorageContextImpl 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();
 
+  // Frees up memory when possible. Purges caches and schedules commits
+  // depending on the given |purge_option|.
+  void PurgeMemory(PurgeOption purge_option);
+
   // base::trace_event::MemoryDumpProvider implementation.
   bool OnMemoryDump(const base::trace_event::MemoryDumpArgs& args,
                     base::trace_event::ProcessMemoryDump* pmd) override;
 
  private:
   friend class DOMStorageContextImplTest;
   FRIEND_TEST_ALL_PREFIXES(DOMStorageContextImplTest, Basics);
   friend class base::RefCountedThreadSafe<DOMStorageContextImpl>;
-  typedef std::map<int64_t, scoped_refptr<DOMStorageNamespace>>
-      StorageNamespaceMap;
 
   ~DOMStorageContextImpl() override;
 
   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);
@@ skipping 33 matching lines @@
   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_;
 
   // Mapping between persistent namespace IDs and namespace IDs for
   // sessionStorage.
   std::map<std::string, int64_t> persistent_namespace_id_to_namespace_id_;
+
+  // For cleaning up unused databases more aggressively.
+  bool is_low_end_device_;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_DOM_STORAGE_DOM_STORAGE_CONTEXT_IMPL_H_