Update from https://crrev.com/320931

base/memory/discardable_memory.h

 // Copyright (c) 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_H_
 #define BASE_MEMORY_DISCARDABLE_MEMORY_H_
 
 #include <string>
 #include <vector>
 
 #include "base/base_export.h"
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
 
 namespace base {
 
-enum DiscardableMemoryType {
-  DISCARDABLE_MEMORY_TYPE_NONE,
-  DISCARDABLE_MEMORY_TYPE_SHMEM
-};
-
 // Platform abstraction for discardable memory. DiscardableMemory is used to
 // cache large objects without worrying about blowing out memory, both on mobile
 // devices where there is no swap, and desktop devices where unused free memory
 // should be used to help the user experience. This is preferable to releasing
 // memory in response to an OOM signal because it is simpler, though it has less
 // flexibility as to which objects get discarded.
 //
 // Discardable memory has two states: locked and unlocked. While the memory is
 // locked, it will not be discarded. Unlocking the memory allows the OS to
 // reclaim it if needed. Locks do not nest.
@@ skipping 15 matching lines @@
 //   - Linux: http://lwn.net/Articles/452035/
 //   - Mac: http://trac.webkit.org/browser/trunk/Source/WebCore/platform/mac/PurgeableBufferMac.cpp
 //          the comment starting with "vm_object_purgable_control" at
 //            http://www.opensource.apple.com/source/xnu/xnu-792.13.8/osfmk/vm/vm_object.c
 //
 // Thread-safety: DiscardableMemory instances are not thread-safe.
 class BASE_EXPORT DiscardableMemory {
  public:
   virtual ~DiscardableMemory() {}
 
-  // Gets the discardable memory type with a given name.
-  static DiscardableMemoryType GetNamedType(const std::string& name);
-
-  // Gets the name of a discardable memory type.
-  static const char* GetTypeName(DiscardableMemoryType type);
-
-  // Gets system supported discardable memory types. Default preferred type
-  // at the front of vector.
-  static void GetSupportedTypes(std::vector<DiscardableMemoryType>* types);
-
-  // Sets the preferred discardable memory type. This overrides the default
-  // preferred type. Can only be called once prior to GetPreferredType()
-  // or CreateLockedMemory(). Caller is responsible for correct ordering.
-  static void SetPreferredType(DiscardableMemoryType type);
-
-  // Gets the preferred discardable memory type.
-  static DiscardableMemoryType GetPreferredType();
-
-  // Create a DiscardableMemory instance with specified |type| and |size|.
-  static scoped_ptr<DiscardableMemory> CreateLockedMemoryWithType(
-      DiscardableMemoryType type, size_t size);
-
-  // Create a DiscardableMemory instance with preferred type and |size|.
+  // Create a DiscardableMemory instance with |size|.
   static scoped_ptr<DiscardableMemory> CreateLockedMemory(size_t size);
 
   // Locks the memory so that it will not be purged by the system. Returns
   // true on success. If the return value is false then this object should be
   // discarded and a new one should be created.
   virtual bool Lock() WARN_UNUSED_RESULT = 0;
 
   // Unlocks the memory so that it can be purged by the system. Must be called
   // after every successful lock call.
   virtual void Unlock() = 0;
 
   // Returns the memory address held by this object. The object must be locked
   // before calling this. Otherwise, this will cause a DCHECK error.
   virtual void* Memory() const = 0;
 };
 
 }  // namespace base
 
 #endif  // BASE_MEMORY_DISCARDABLE_MEMORY_H_