Update from https://crrev.com/320343

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_ASHMEM,
-  DISCARDABLE_MEMORY_TYPE_MACH,
-  DISCARDABLE_MEMORY_TYPE_EMULATED,
   DISCARDABLE_MEMORY_TYPE_SHMEM
 };
 
-enum DiscardableMemoryLockStatus {
-  DISCARDABLE_MEMORY_LOCK_STATUS_FAILED,
-  DISCARDABLE_MEMORY_LOCK_STATUS_PURGED,
-  DISCARDABLE_MEMORY_LOCK_STATUS_SUCCESS
-};
-
 // 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 40 matching lines @@
   // 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|.
   static scoped_ptr<DiscardableMemory> CreateLockedMemory(size_t size);
 
-  // Discardable memory implementations might allow an elevated usage level
-  // while in frequent use. Call this to have the usage reduced to the base
-  // level. Returns true if there's no need to call this again until
-  // memory instances have been used. This indicates that all discardable
-  // memory implementations have reduced usage to the base level or below.
-  // Note: calling this too often or while discardable memory is in frequent
-  // use can hurt performance, whereas calling it too infrequently can result
-  // in memory bloat.
-  static bool ReduceMemoryUsage();
-
   // Locks the memory so that it will not be purged by the system. Returns
-  // DISCARDABLE_MEMORY_LOCK_STATUS_SUCCESS on success. If the return value is
-  // DISCARDABLE_MEMORY_LOCK_STATUS_FAILED then this object should be
-  // discarded and a new one should be created. If the return value is
-  // DISCARDABLE_MEMORY_LOCK_STATUS_PURGED then the memory is present but any
-  // data that was in it is gone.
-  virtual DiscardableMemoryLockStatus Lock() WARN_UNUSED_RESULT = 0;
+  // 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_