Purge new localstorage memory cache when under memory pressure.

content/browser/leveldb_wrapper_impl.h

 // Copyright 2016 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_LEVELDB_WRAPPER_IMPL_H_
 #define CONTENT_BROWSER_LEVELDB_WRAPPER_IMPL_H_
 
 #include <map>
 #include <memory>
 #include <string>
@@ skipping 56 matching lines @@
   // rescheduled and will be flushed at the scheduled time after which
   // aggressive flushing will commence.
   static void EnableAggressiveCommitDelay();
 
   // Commits any uncommitted data to the database as soon as possible. This
   // usually means data will be committed immediately, but if we're currently
   // waiting on the result of initializing our map the commit won't happen
   // until the load has finished.
   void ScheduleImmediateCommit();
 
+  // Clears the in-memory cache if currently no changes are pending. If there
+  // are uncommitted changes this method does nothing.
+  void PurgeMemory();
+
   // LevelDBWrapper:
   void AddObserver(mojom::LevelDBObserverAssociatedPtrInfo observer) override;
   void Put(const std::vector<uint8_t>& key,
            const std::vector<uint8_t>& value,
            const std::string& source,
            const PutCallback& callback) override;
   void Delete(const std::vector<uint8_t>& key,
               const std::string& source,
               const DeleteCallback& callback) override;
   void DeleteAll(const std::string& source,
@@ skipping 66 matching lines @@
   base::WeakPtrFactory<LevelDBWrapperImpl> weak_ptr_factory_;
 
   static bool s_aggressive_flushing_enabled_;
 
   DISALLOW_COPY_AND_ASSIGN(LevelDBWrapperImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_LEVELDB_WRAPPER_IMPL_H_