Re-land: base: Introduce an explicit call for reducing emulated discardable memory usage.

base/memory/discardable_memory_android.cc

Index: base/memory/discardable_memory_android.cc
diff --git a/base/memory/discardable_memory_android.cc b/base/memory/discardable_memory_android.cc
index 8988c2b8d2bd46d759ec2f9c42243b6274d114be..03dae34aac6a3dca182a02a5042cda48782b5d19 100644
--- a/base/memory/discardable_memory_android.cc
+++ b/base/memory/discardable_memory_android.cc
@@ -47,16 +47,6 @@ LazyInstance<SharedState>::Leaky g_shared_state = LAZY_INSTANCE_INITIALIZER;
 }  // namespace
 
 // static
-void DiscardableMemory::RegisterMemoryPressureListeners() {
-  internal::DiscardableMemoryEmulated::RegisterMemoryPressureListeners();
-}
-
-// static
-void DiscardableMemory::UnregisterMemoryPressureListeners() {
-  internal::DiscardableMemoryEmulated::UnregisterMemoryPressureListeners();
-}
-
-// static
 bool DiscardableMemory::ReduceMemoryUsage() {
   return internal::DiscardableMemoryEmulated::ReduceMemoryUsage();
 }