Make memory pressure notifier configurable

base/memory/memory_pressure_monitor_mac.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/memory/memory_pressure_monitor_mac.h"
 
 #include <dlfcn.h>
 #include <stddef.h>
 #include <sys/sysctl.h>
 
@@ skipping 14 matching lines @@
       return MemoryPressureListener::MEMORY_PRESSURE_LEVEL_CRITICAL;
   }
   return MemoryPressureListener::MEMORY_PRESSURE_LEVEL_NONE;
 }
 
 void MemoryPressureMonitor::NotifyMemoryPressureChanged(
     dispatch_source_s* event_source) {
   int mac_memory_pressure = dispatch_source_get_data(event_source);
   MemoryPressureListener::MemoryPressureLevel memory_pressure_level =
       MemoryPressureLevelForMacMemoryPressure(mac_memory_pressure);
-  MemoryPressureListener::NotifyMemoryPressure(memory_pressure_level);
+  MemoryPressureMonitor::Get()->Notify(memory_pressure_level);
 }
 
 MemoryPressureMonitor::MemoryPressureMonitor()
   : memory_level_event_source_(nullptr) {
   // _dispatch_source_type_memorypressure is not available prior to 10.9.
   dispatch_source_type_t dispatch_source_memorypressure =
       static_cast<dispatch_source_type_t>
           (dlsym(RTLD_NEXT, "_dispatch_source_type_memorypressure"));
   if (dispatch_source_memorypressure) {
     // The MemoryPressureListener doesn't want to know about transitions to
@@ skipping 21 matching lines @@
 MemoryPressureMonitor::GetCurrentPressureLevel() const {
   int mac_memory_pressure;
   size_t length = sizeof(int);
   sysctlbyname("kern.memorystatus_vm_pressure_level", &mac_memory_pressure,
                &length, nullptr, 0);
   return MemoryPressureLevelForMacMemoryPressure(mac_memory_pressure);
 }
 
 }  // namespace mac
 }  // namespace base