base: Remove non-caching discardable memory implementation.

base/memory/discardable_memory_malloc.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 BASE_MEMORY_DISCARDABLE_MEMORY_MALLOC_H_
-#define BASE_MEMORY_DISCARDABLE_MEMORY_MALLOC_H_
-
-#include "base/memory/discardable_memory.h"
-
-namespace base {
-namespace internal {
-
-class DiscardableMemoryMalloc : public DiscardableMemory {
- public:
-  explicit DiscardableMemoryMalloc(size_t size);
-  virtual ~DiscardableMemoryMalloc();
-
-  bool Initialize();
-
-  // Overridden from DiscardableMemory:
-  virtual DiscardableMemoryLockStatus Lock() override;
-  virtual void Unlock() override;
-  virtual void* Memory() const override;
-
- private:
-  scoped_ptr<uint8, FreeDeleter> memory_;
-  const size_t size_;
-
-  DISALLOW_COPY_AND_ASSIGN(DiscardableMemoryMalloc);
-};
-
-}  // namespace internal
-}  // namespace base
-
-#endif  // BASE_MEMORY_DISCARDABLE_MEMORY_MALLOC_H_