Purge browser cache for dom storage in a smarter way

content/browser/dom_storage/dom_storage_context_wrapper.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_CONTEXT_WRAPPER_H_
 #define CONTENT_BROWSER_DOM_STORAGE_DOM_STORAGE_CONTEXT_WRAPPER_H_
 
 #include <map>
 #include <string>
 
 #include "base/macros.h"
+#include "base/memory/memory_pressure_listener.h"
 #include "base/memory/ref_counted.h"
 #include "content/common/content_export.h"
 #include "content/common/storage_partition_service.mojom.h"
 #include "content/public/browser/dom_storage_context.h"
 #include "url/origin.h"
 
 namespace base {
 class FilePath;
 }
 
@@ skipping 44 matching lines @@
   // Called when the BrowserContext/Profile is going away.
   void Shutdown();
 
   void Flush();
 
   // See mojom::StoragePartitionService interface.
   void OpenLocalStorage(const url::Origin& origin,
                         mojom::LevelDBObserverPtr observer,
                         mojom::LevelDBWrapperRequest request);
 
+  // Called on UI thread when the system is under memory pressure.
+  void OnMemoryPressure(
+      base::MemoryPressureListener::MemoryPressureLevel memory_pressure_level);
+
  private:
   friend class DOMStorageMessageFilter;  // for access to context()
   friend class SessionStorageNamespaceImpl;  // ditto
   friend class base::RefCountedThreadSafe<DOMStorageContextWrapper>;
 
   ~DOMStorageContextWrapper() override;
   DOMStorageContextImpl* context() const { return context_.get(); }
 
   // An inner class to keep all mojo-ish details together and not bleed them
   // through the public interface.
   class MojoState;
   std::unique_ptr<MojoState> mojo_state_;
 
+  // To receive memory pressure signals.
+  std::unique_ptr<base::MemoryPressureListener> memory_pressure_listener_;
+
   scoped_refptr<DOMStorageContextImpl> context_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(DOMStorageContextWrapper);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_DOM_STORAGE_DOM_STORAGE_CONTEXT_WRAPPER_H_