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>
 #include <set>
 #include <string>
 #include <vector>
 
 #include "base/atomic_sequence_num.h"
 #include "base/files/file_path.h"
 #include "base/gtest_prod_util.h"
+#include "base/memory/memory_pressure_listener.h"
 #include "base/memory/ref_counted.h"
 #include "base/observer_list.h"
 #include "base/time/time.h"
 #include "base/trace_event/memory_dump_provider.h"
 #include "content/common/content_export.h"
 #include "url/gurl.h"
 
 namespace base {
 class FilePath;
 class NullableString16;
@@ skipping 140 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();
 
+  // Called on the |task_runner| to purge memory in case of memory pressure.
+  void PurgeMemory(
+      base::MemoryPressureListener::MemoryPressureLevel memory_pressure_level);
+
   // base::trace_event::MemoryDumpProvider implementation.
   bool OnMemoryDump(const base::trace_event::MemoryDumpArgs& args,
                     base::trace_event::ProcessMemoryDump* pmd) override;
 
  private:
+  class DOMStorageMemoryPressureListener;
   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();
 
@@ skipping 38 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_;
+
+  // Notifier for memory pressure signals to purges memory.
+  DOMStorageMemoryPressureListener* leaked_memory_pressure_listener_;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_DOM_STORAGE_DOM_STORAGE_CONTEXT_IMPL_H_