memory coordinator: Add MemoryCoordinatorClient::OnPurgeMemory()

components/discardable_memory/service/discardable_shared_memory_manager.h

 // Copyright 2014 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 COMPONENTS_DISCARDABLE_MEMORY_SERVICE_DISCARDABLE_SHARED_MEMORY_MANAGER_H_
 #define COMPONENTS_DISCARDABLE_MEMORY_SERVICE_DISCARDABLE_SHARED_MEMORY_MANAGER_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 89 matching lines @@
   };
 
   static bool CompareMemoryUsageTime(const scoped_refptr<MemorySegment>& a,
                                      const scoped_refptr<MemorySegment>& b) {
     // In this system, LRU memory segment is evicted first.
     return a->memory()->last_known_usage() > b->memory()->last_known_usage();
   }
 
   // base::MemoryCoordinatorClient implementation:
   void OnMemoryStateChange(base::MemoryState state) override;
+  void OnPurgeMemory() override;
 
   void AllocateLockedDiscardableSharedMemory(
       int client_id,
       size_t size,
       int32_t id,
       base::SharedMemoryHandle* shared_memory_handle);
   void DeletedDiscardableSharedMemory(int32_t id, int client_id);
   void OnMemoryPressure(
       base::MemoryPressureListener::MemoryPressureLevel memory_pressure_level);
   void ReduceMemoryUsageUntilWithinMemoryLimit();
@@ skipping 25 matching lines @@
   base::Closure enforce_memory_policy_callback_;
   bool enforce_memory_policy_pending_;
   base::WeakPtrFactory<DiscardableSharedMemoryManager> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(DiscardableSharedMemoryManager);
 };
 
 }  // namespace discardable_memory
 
 #endif  // COMPONENTS_DISCARDABLE_MEMORY_SERVICE_DISCARDABLE_SHARED_MEMORY_MANAGER_H_