Re-land: base: Fix registering of memory pressure listeners used when emulating discardable memory.

base/memory/discardable_memory_emulated.cc

 // Copyright 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_emulated.h"
 
 #include "base/lazy_instance.h"
 #include "base/memory/discardable_memory_provider.h"
 
 namespace base {
@@ skipping 11 matching lines @@
     : is_locked_(false) {
   g_provider.Pointer()->Register(this, size);
 }
 
 DiscardableMemoryEmulated::~DiscardableMemoryEmulated() {
   if (is_locked_)
     Unlock();
   g_provider.Pointer()->Unregister(this);
 }
 
+// static
+void DiscardableMemoryEmulated::RegisterMemoryPressureListeners() {
+  g_provider.Pointer()->RegisterMemoryPressureListener();
+}
+
+// static
+void DiscardableMemoryEmulated::UnregisterMemoryPressureListeners() {
+  g_provider.Pointer()->UnregisterMemoryPressureListener();
+}
+
+// static
+void DiscardableMemoryEmulated::PurgeForTesting() {
+  g_provider.Pointer()->PurgeAll();
+}
+
 bool DiscardableMemoryEmulated::Initialize() {
   return Lock() == DISCARDABLE_MEMORY_LOCK_STATUS_PURGED;
 }
 
 DiscardableMemoryLockStatus DiscardableMemoryEmulated::Lock() {
   DCHECK(!is_locked_);
 
   bool purged = false;
   memory_ = g_provider.Pointer()->Acquire(this, &purged);
   if (!memory_)
     return DISCARDABLE_MEMORY_LOCK_STATUS_FAILED;
 
   is_locked_ = true;
   return purged ? DISCARDABLE_MEMORY_LOCK_STATUS_PURGED
                 : DISCARDABLE_MEMORY_LOCK_STATUS_SUCCESS;
 }
 
 void DiscardableMemoryEmulated::Unlock() {
   DCHECK(is_locked_);
   g_provider.Pointer()->Release(this, memory_.Pass());
   is_locked_ = false;
 }
 
 void* DiscardableMemoryEmulated::Memory() const {
   DCHECK(memory_);
   return memory_.get();
 }
 
-// static
-void DiscardableMemoryEmulated::PurgeForTesting() {
-  g_provider.Pointer()->PurgeAll();
-}
-
 }  // namespace internal
 }  // namespace base