Revert of Use DiscardableMemoryManager on Android.

base/memory/discardable_memory_ashmem_allocator.h

-// Copyright 2013 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 BASE_MEMORY_DISCARDABLE_MEMORY_ASHMEM_ALLOCATOR_H_
-#define BASE_MEMORY_DISCARDABLE_MEMORY_ASHMEM_ALLOCATOR_H_
-
-#include <string>
-
-#include "base/base_export.h"
-#include "base/basictypes.h"
-#include "base/memory/scoped_ptr.h"
-#include "base/memory/scoped_vector.h"
-#include "base/synchronization/lock.h"
-
-namespace base {
-namespace internal {
-
-class AshmemRegion;
-
-// Internal class, whose instances are returned to the client of the allocator
-// (e.g. DiscardableMemoryAshmem), that mimicks the DiscardableMemory interface.
-class BASE_EXPORT_PRIVATE DiscardableAshmemChunk {
- public:
-  ~DiscardableAshmemChunk();
-
-  // Returns whether the memory is still resident.
-  bool Lock();
-
-  void Unlock();
-
-  void* Memory() const;
-
- private:
-  friend class AshmemRegion;
-
-  DiscardableAshmemChunk(AshmemRegion* ashmem_region,
-                         int fd,
-                         void* address,
-                         size_t offset,
-                         size_t size);
-
-  AshmemRegion* const ashmem_region_;
-  const int fd_;
-  void* const address_;
-  const size_t offset_;
-  const size_t size_;
-  bool locked_;
-
-  DISALLOW_COPY_AND_ASSIGN(DiscardableAshmemChunk);
-};
-
-// Ashmem regions are backed by a file (descriptor) therefore they are a limited
-// resource. This allocator minimizes the problem by allocating large ashmem
-// regions internally and returning smaller chunks to the client.
-// Allocated chunks are systematically aligned on a page boundary therefore this
-// allocator should not be used for small allocations.
-class BASE_EXPORT_PRIVATE DiscardableMemoryAshmemAllocator {
- public:
-  // Note that |name| is only used for debugging/measurement purposes.
-  // |ashmem_region_size| is the size that will be used to create the underlying
-  // ashmem regions and is expected to be greater or equal than 32 MBytes.
-  DiscardableMemoryAshmemAllocator(const std::string& name,
-                                   size_t ashmem_region_size);
-
-  ~DiscardableMemoryAshmemAllocator();
-
-  // Note that the allocator must outlive the returned DiscardableAshmemChunk
-  // instance.
-  scoped_ptr<DiscardableAshmemChunk> Allocate(size_t size);
-
-  // Returns the size of the last ashmem region which was created. This is used
-  // for testing only.
-  size_t last_ashmem_region_size() const;
-
- private:
-  friend class AshmemRegion;
-
-  void DeleteAshmemRegion_Locked(AshmemRegion* region);
-
-  const std::string name_;
-  const size_t ashmem_region_size_;
-  mutable Lock lock_;
-  size_t last_ashmem_region_size_;
-  ScopedVector<AshmemRegion> ashmem_regions_;
-
-  DISALLOW_COPY_AND_ASSIGN(DiscardableMemoryAshmemAllocator);
-};
-
-}  // namespace internal
-}  // namespace base
-
-#endif  // BASE_MEMORY_DISCARDABLE_MEMORY_ASHMEM_ALLOCATOR_H_