content: Release all free discardable memory when idle.

content/child/child_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 CONTENT_CHILD_CHILD_DISCARDABLE_SHARED_MEMORY_MANAGER_H_
 #define CONTENT_CHILD_CHILD_DISCARDABLE_SHARED_MEMORY_MANAGER_H_
 
 #include "base/memory/discardable_memory_shmem_allocator.h"
 #include "base/memory/ref_counted.h"
 #include "base/synchronization/lock.h"
@@ skipping 18 matching lines @@
   // Release memory and associated resources that have been purged.
   void ReleaseFreeMemory();
 
   bool LockSpan(DiscardableSharedMemoryHeap::Span* span);
   void UnlockSpan(DiscardableSharedMemoryHeap::Span* span);
   void ReleaseSpan(scoped_ptr<DiscardableSharedMemoryHeap::Span> span);
 
  private:
   scoped_ptr<base::DiscardableSharedMemory>
   AllocateLockedDiscardableSharedMemory(size_t size);
-  void BytesAllocatedChanged(size_t new_bytes_allocated) const;
+  void MemoryUsageChanged(size_t new_bytes_allocated,
+                          size_t new_bytes_free) const;
 
   mutable base::Lock lock_;
   DiscardableSharedMemoryHeap heap_;
   scoped_refptr<ThreadSafeSender> sender_;
-  size_t bytes_allocated_;
 
   DISALLOW_COPY_AND_ASSIGN(ChildDiscardableSharedMemoryManager);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_CHILD_CHILD_DISCARDABLE_SHARED_MEMORY_MANAGER_H_