base: Add free list implementation to browser-wide discardable memory system.

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"
 #include "content/child/thread_safe_sender.h"
+#include "content/common/discardable_shared_memory_heap.h"
 
 namespace content {
 
 // Implementation of DiscardableMemoryShmemAllocator that allocates
 // discardable memory segments through the browser process.
 class ChildDiscardableSharedMemoryManager
     : public base::DiscardableMemoryShmemAllocator {
  public:
   explicit ChildDiscardableSharedMemoryManager(ThreadSafeSender* sender);
   ~ChildDiscardableSharedMemoryManager() override;
 
   // Overridden from base::DiscardableMemoryShmemAllocator:
-  scoped_ptr<base::DiscardableSharedMemory>
-  AllocateLockedDiscardableSharedMemory(size_t size) override;
+  scoped_ptr<base::DiscardableMemoryShmemChunk> AllocateLockedDiscardableMemory(
+      size_t size) override;
+
+  bool LockSpan(DiscardableSharedMemoryHeap::Span* span);
+  void UnlockSpan(DiscardableSharedMemoryHeap::Span* span);
+  bool IsSpanResident(DiscardableSharedMemoryHeap::Span* span) const;
+  void ReleaseSpan(scoped_ptr<DiscardableSharedMemoryHeap::Span> span);
 
  private:
+  scoped_ptr<base::DiscardableSharedMemory>
+  AllocateLockedDiscardableSharedMemory(size_t size);
+
+  mutable base::Lock lock_;
+  DiscardableSharedMemoryHeap heap_;
   scoped_refptr<ThreadSafeSender> sender_;
 
   DISALLOW_COPY_AND_ASSIGN(ChildDiscardableSharedMemoryManager);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_CHILD_CHILD_DISCARDABLE_SHARED_MEMORY_MANAGER_H_