Update from https://crrev.com/320343

base/memory/discardable_memory_android.cc

 // 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.
 
 #include "base/memory/discardable_memory.h"
 
-#include "base/basictypes.h"
-#include "base/compiler_specific.h"
-#include "base/lazy_instance.h"
 #include "base/logging.h"
-#include "base/memory/discardable_memory_ashmem.h"
-#include "base/memory/discardable_memory_ashmem_allocator.h"
-#include "base/memory/discardable_memory_emulated.h"
 #include "base/memory/discardable_memory_shmem.h"
-#include "base/sys_info.h"
 
 namespace base {
-namespace {
-
-const char kAshmemAllocatorName[] = "DiscardableMemoryAshmemAllocator";
-
-// For Ashmem, have the DiscardableMemoryManager trigger userspace eviction
-// when address space usage gets too high (e.g. 512 MBytes).
-const size_t kAshmemMemoryLimit = 512 * 1024 * 1024;
-
-size_t GetOptimalAshmemRegionSizeForAllocator() {
-  // Note that this may do some I/O (without hitting the disk though) so it
-  // should not be called on the critical path.
-  return base::SysInfo::AmountOfPhysicalMemory() / 8;
-}
-
-// Holds the shared state used for allocations.
-struct SharedState {
-  SharedState()
-      : manager(kAshmemMemoryLimit, kAshmemMemoryLimit, TimeDelta::Max()),
-        allocator(kAshmemAllocatorName,
-                  GetOptimalAshmemRegionSizeForAllocator()) {}
-
-  internal::DiscardableMemoryManager manager;
-  internal::DiscardableMemoryAshmemAllocator allocator;
-};
-LazyInstance<SharedState>::Leaky g_shared_state = LAZY_INSTANCE_INITIALIZER;
-
-}  // namespace
-
-// static
-bool DiscardableMemory::ReduceMemoryUsage() {
-  return internal::DiscardableMemoryEmulated::ReduceMemoryUsage();
-}
 
 // static
 void DiscardableMemory::GetSupportedTypes(
     std::vector<DiscardableMemoryType>* types) {
   const DiscardableMemoryType supported_types[] = {
-    DISCARDABLE_MEMORY_TYPE_SHMEM,
-    DISCARDABLE_MEMORY_TYPE_ASHMEM,
-    DISCARDABLE_MEMORY_TYPE_EMULATED
+    DISCARDABLE_MEMORY_TYPE_SHMEM
   };
   types->assign(supported_types, supported_types + arraysize(supported_types));
 }
 
 // static
 scoped_ptr<DiscardableMemory> DiscardableMemory::CreateLockedMemoryWithType(
     DiscardableMemoryType type, size_t size) {
   switch (type) {
-    case DISCARDABLE_MEMORY_TYPE_ASHMEM: {
-      SharedState* const shared_state = g_shared_state.Pointer();
-      scoped_ptr<internal::DiscardableMemoryAshmem> memory(
-          new internal::DiscardableMemoryAshmem(
-              size, &shared_state->allocator, &shared_state->manager));
-      if (!memory->Initialize())
-        return nullptr;
-
-      return memory.Pass();
-    }
-    case DISCARDABLE_MEMORY_TYPE_EMULATED: {
-      scoped_ptr<internal::DiscardableMemoryEmulated> memory(
-          new internal::DiscardableMemoryEmulated(size));
-      if (!memory->Initialize())
-        return nullptr;
-
-      return memory.Pass();
-    }
-    case DISCARDABLE_MEMORY_TYPE_SHMEM: {
-      scoped_ptr<internal::DiscardableMemoryShmem> memory(
-          new internal::DiscardableMemoryShmem(size));
-      if (!memory->Initialize())
-        return nullptr;
-
-      return memory.Pass();
-    }
+    case DISCARDABLE_MEMORY_TYPE_SHMEM:
+      return make_scoped_ptr(new internal::DiscardableMemoryShmem(size));
     case DISCARDABLE_MEMORY_TYPE_NONE:
-    case DISCARDABLE_MEMORY_TYPE_MACH:
       NOTREACHED();
       return nullptr;
   }
 
   NOTREACHED();
   return nullptr;
 }
 
 }  // namespace base