Update from https://crrev.com/316786

base/memory/discardable_memory_shmem.h

Index: base/memory/discardable_memory_shmem.h
diff --git a/base/memory/discardable_memory_shmem.h b/base/memory/discardable_memory_shmem.h
index b04c9b1ea6ebe70fb79af1f4f01be675749cc6f7..98d3b97a204a4fe11ec0933aee7e5e877c1de2a9 100644
--- a/base/memory/discardable_memory_shmem.h
+++ b/base/memory/discardable_memory_shmem.h
@@ -7,24 +7,16 @@
 
 #include "base/memory/discardable_memory.h"
 
-#include "base/memory/discardable_memory_manager.h"
-
 namespace base {
 class DiscardableMemoryShmemChunk;
 
 namespace internal {
 
-class DiscardableMemoryShmem
-    : public DiscardableMemory,
-      public internal::DiscardableMemoryManagerAllocation {
+class DiscardableMemoryShmem : public DiscardableMemory {
  public:
   explicit DiscardableMemoryShmem(size_t bytes);
   ~DiscardableMemoryShmem() override;
 
-  static void ReleaseFreeMemory();
-
-  static void PurgeForTesting();
-
   bool Initialize();
 
   // Overridden from DiscardableMemory:
@@ -32,12 +24,6 @@ class DiscardableMemoryShmem
   void Unlock() override;
   void* Memory() const override;
 
-  // Overridden from internal::DiscardableMemoryManagerAllocation:
-  bool AllocateAndAcquireLock() override;
-  void ReleaseLock() override;
-  void Purge() override;
-  bool IsMemoryResident() const override;
-
  private:
   const size_t bytes_;
   scoped_ptr<DiscardableMemoryShmemChunk> chunk_;