[Mac] Return cached pressure level in GetCurrentPressureLevel().

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 <CoreFoundation/CoreFoundation.h>
 
 #include <dlfcn.h>
 #include <stddef.h>
@@ skipping 144 matching lines @@
   }
 }
 
 // Static.
 int MemoryPressureMonitor::GetSecondsPerUMATick() {
   return kUMATickSize;
 }
 
 MemoryPressureListener::MemoryPressureLevel
 MemoryPressureMonitor::GetCurrentPressureLevel() {
-  UpdatePressureLevel();
   return last_pressure_level_;
 }
 
 void MemoryPressureMonitor::OnMemoryPressureChanged(
     dispatch_source_s* event_source,
     const MemoryPressureMonitor::DispatchCallback& dispatch_callback) {
   // Get the Chrome-equvialent memory pressure level.
   int mac_memory_pressure_level = dispatch_source_get_data(event_source);
   MemoryPressureListener::MemoryPressureLevel memory_pressure_level =
       MemoryPressureLevelForMacMemoryPressureLevel(mac_memory_pressure_level);
@@ skipping 15 matching lines @@
     dispatch_callback.Run(memory_pressure_level);
 }
 
 void MemoryPressureMonitor::SetDispatchCallback(
     const DispatchCallback& callback) {
   dispatch_callback_ = callback;
 }
 
 }  // namespace mac
 }  // namespace base