Update from https://crrev.com/316786

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>
 
@@ skipping 71 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 use this to release memory
-  // or resources assigned to instances that have been purged.
-  static void ReleaseFreeMemory();
-
   // 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;
 
   // 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;
-
-  // Testing utility calls.
-
-  // Purge all discardable memory in the system. This call has global effects
-  // across all running processes, so it should only be used for testing!
-  static void PurgeForTesting();
 };
 
 }  // namespace base
 
 #endif  // BASE_MEMORY_DISCARDABLE_MEMORY_H_