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

base/memory/discardable_memory_linux.cc

Index: base/memory/discardable_memory_linux.cc
diff --git a/base/memory/discardable_memory_linux.cc b/base/memory/discardable_memory_linux.cc
index b9342e92043cad68ba0470e201e35d94d116613a..578b2c1c756049559e902300dffe1ddf51a82635 100644
--- a/base/memory/discardable_memory_linux.cc
+++ b/base/memory/discardable_memory_linux.cc
@@ -11,16 +11,6 @@
 namespace base {
 
 // static
-void DiscardableMemory::RegisterMemoryPressureListeners() {
-  internal::DiscardableMemoryEmulated::RegisterMemoryPressureListeners();
-}
-
-// static
-void DiscardableMemory::UnregisterMemoryPressureListeners() {
-  internal::DiscardableMemoryEmulated::UnregisterMemoryPressureListeners();
-}
-
-// static
 bool DiscardableMemory::ReduceMemoryUsage() {
   return internal::DiscardableMemoryEmulated::ReduceMemoryUsage();
 }