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

base/memory/discardable_memory_mac.cc

Index: base/memory/discardable_memory_mac.cc
diff --git a/base/memory/discardable_memory_mac.cc b/base/memory/discardable_memory_mac.cc
index 6f8cc42d85e6d517abee826756c960e995251f3c..0c0b2a60add086856647343be5b1998c40dc8359 100644
--- a/base/memory/discardable_memory_mac.cc
+++ b/base/memory/discardable_memory_mac.cc
@@ -89,6 +89,16 @@ class DiscardableMemoryMac : public DiscardableMemory {
 }  // namespace
 
 // static
+void DiscardableMemory::RegisterMemoryPressureListeners() {
+  internal::DiscardableMemoryEmulated::RegisterMemoryPressureListeners();
+}
+
+// static
+void DiscardableMemory::UnregisterMemoryPressureListeners() {
+  internal::DiscardableMemoryEmulated::UnregisterMemoryPressureListeners();
+}
+
+// static
 void DiscardableMemory::GetSupportedTypes(
     std::vector<DiscardableMemoryType>* types) {
   const DiscardableMemoryType supported_types[] = {