Revert 239763 "Add DiscardableMemoryAllocator to minimize use of..."

trunk/src/base/memory/discardable_memory_allocator_android.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_ALLOCATOR_H_
-#define BASE_MEMORY_DISCARDABLE_MEMORY_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"
-#include "base/threading/thread_checker.h"
-
-namespace base {
-
-class DiscardableMemory;
-
-namespace internal {
-
-// On Android ashmem is used to implement discardable memory. It is backed by a
-// file (descriptor) thus is 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.
-//
-// Threading: The allocator must be deleted on the thread it was constructed on
-// although its Allocate() method can be invoked on any thread. See
-// discardable_memory.h for DiscardableMemory's threading guarantees.
-class BASE_EXPORT_PRIVATE DiscardableMemoryAllocator {
- public:
-  // Exposed for testing.
-  enum {
-    kMinAshmemRegionSize = 32 * 1024 * 1024,
-  };
-
-  // Note that |name| is only used for debugging/measurement purposes.
-  explicit DiscardableMemoryAllocator(const std::string& name);
-  ~DiscardableMemoryAllocator();
-
-  // Note that the allocator must outlive the returned DiscardableMemory
-  // instance.
-  scoped_ptr<DiscardableMemory> Allocate(size_t size);
-
- private:
-  class AshmemRegion;
-  class DiscardableAshmemChunk;
-
-  void DeleteAshmemRegion_Locked(AshmemRegion* region);
-
-  base::ThreadChecker thread_checker_;
-  const std::string name_;
-  base::Lock lock_;
-  ScopedVector<AshmemRegion> ashmem_regions_;
-
-  DISALLOW_COPY_AND_ASSIGN(DiscardableMemoryAllocator);
-};
-
-}  // namespace internal
-}  // namespace base
-
-#endif  // BASE_MEMORY_DISCARDABLE_MEMORY_ALLOCATOR_H_