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

base/memory/discardable_memory_emulated.cc

Index: base/memory/discardable_memory_emulated.cc
diff --git a/base/memory/discardable_memory_emulated.cc b/base/memory/discardable_memory_emulated.cc
index af4bf39b7677e5d93655ef7bf550b4e5c9e878da..be756d6fc9cb94ee34aed5016100750778b79c30 100644
--- a/base/memory/discardable_memory_emulated.cc
+++ b/base/memory/discardable_memory_emulated.cc
@@ -29,6 +29,21 @@ DiscardableMemoryEmulated::~DiscardableMemoryEmulated() {
   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;
 }
@@ -57,10 +72,5 @@ void* DiscardableMemoryEmulated::Memory() const {
   return memory_.get();
 }
 
-// static
-void DiscardableMemoryEmulated::PurgeForTesting() {
-  g_provider.Pointer()->PurgeAll();
-}
-
 }  // namespace internal
 }  // namespace base