Update from https://crrev.com/320343

base/memory/discardable_memory.h

Index: base/memory/discardable_memory.h
diff --git a/base/memory/discardable_memory.h b/base/memory/discardable_memory.h
index c49a99f7a8c78af772cce254b1aca081dea6d15e..4e5a9af7aa5b3f5b88bd3747dc1b0c7542aad522 100644
--- a/base/memory/discardable_memory.h
+++ b/base/memory/discardable_memory.h
@@ -17,18 +17,9 @@ 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
@@ -89,23 +80,10 @@ class BASE_EXPORT DiscardableMemory {
   // 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.