Move purging from OnMemoryState to OnPurgeMemory() in cc/

cc/raster/staging_buffer_pool.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 CC_RASTER_STAGING_BUFFER_POOL_H_
 #define CC_RASTER_STAGING_BUFFER_POOL_H_
 
 #include <stdint.h>
 
 #include <deque>
@@ skipping 73 matching lines @@
   void ReduceMemoryUsage();
   void ReleaseBuffersNotUsedSince(base::TimeTicks time);
 
   std::unique_ptr<base::trace_event::ConvertableToTraceFormat> StateAsValue()
       const;
   void StagingStateAsValueInto(
       base::trace_event::TracedValue* staging_state) const;
 
   // Overriden from base::MemoryCoordinatorClient.
   void OnMemoryStateChange(base::MemoryState state) override;
+  void OnPurgeMemory() override;
 
   scoped_refptr<base::SequencedTaskRunner> task_runner_;
   ContextProvider* const worker_context_provider_;
   ResourceProvider* const resource_provider_;
   const bool use_partial_raster_;
 
   mutable base::Lock lock_;
   // |lock_| must be acquired when accessing the following members.
   using StagingBufferSet = std::set<const StagingBuffer*>;
   StagingBufferSet buffers_;
   using StagingBufferDeque = std::deque<std::unique_ptr<StagingBuffer>>;
   StagingBufferDeque free_buffers_;
   StagingBufferDeque busy_buffers_;
   const int max_staging_buffer_usage_in_bytes_;
   int staging_buffer_usage_in_bytes_;
   int free_staging_buffer_usage_in_bytes_;
   const base::TimeDelta staging_buffer_expiration_delay_;
   bool reduce_memory_usage_pending_;
   base::Closure reduce_memory_usage_callback_;
 
   base::WeakPtrFactory<StagingBufferPool> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(StagingBufferPool);
 };
 
 }  // namespace cc
 
 #endif  // CC_RASTER_STAGING_BUFFER_POOL_H_