Update from https://crrev.com/316786

base/memory/discardable_memory_mach.cc

Index: base/memory/discardable_memory_mach.cc
diff --git a/base/memory/discardable_memory_mach.cc b/base/memory/discardable_memory_mach.cc
index 5fc43f2a7d850e487cae1f339adb89211a6281f4..d96de79121b79433cf0a0590008f46c2848d2298 100644
--- a/base/memory/discardable_memory_mach.cc
+++ b/base/memory/discardable_memory_mach.cc
@@ -63,12 +63,6 @@ DiscardableMemoryMach::~DiscardableMemoryMach() {
   g_manager.Pointer()->Unregister(this);
 }
 
-// static
-void DiscardableMemoryMach::PurgeForTesting() {
-  int state = 0;
-  vm_purgable_control(mach_task_self(), 0, VM_PURGABLE_PURGE_ALL, &state);
-}
-
 bool DiscardableMemoryMach::Initialize() {
   return Lock() != DISCARDABLE_MEMORY_LOCK_STATUS_FAILED;
 }
@@ -154,9 +148,5 @@ void DiscardableMemoryMach::Purge() {
   memory_.reset();
 }
 
-bool DiscardableMemoryMach::IsMemoryResident() const {
-  return true;
-}
-
 }  // namespace internal
 }  // namespace base