base: Add uncached malloc based discardable memory type.

base/memory/discardable_memory_malloc.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_EMULATED_H_
-#define BASE_MEMORY_DISCARDABLE_MEMORY_EMULATED_H_
+#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 DiscardableMemoryEmulated : public DiscardableMemory {
+class DiscardableMemoryMalloc : public DiscardableMemory {
  public:
-  explicit DiscardableMemoryEmulated(size_t size);
-  virtual ~DiscardableMemoryEmulated();
-
-  static void RegisterMemoryPressureListeners();
-  static void UnregisterMemoryPressureListeners();
-
-  static void PurgeForTesting();
+  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_;
-  bool is_locked_;
+  const size_t size_;
 
-  DISALLOW_COPY_AND_ASSIGN(DiscardableMemoryEmulated);
+  DISALLOW_COPY_AND_ASSIGN(DiscardableMemoryMalloc);
 };
 
 }  // namespace internal
 }  // namespace base
 
-#endif  // BASE_MEMORY_DISCARDABLE_MEMORY_EMULATED_H_
+#endif  // BASE_MEMORY_DISCARDABLE_MEMORY_MALLOC_H_