[Mac] Report statistics more regularly in Mac memory pressure monitor

base/memory/memory_pressure_monitor_win.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_win.h"
 
 #include <windows.h>
 
 #include "base/single_thread_task_runner.h"
 #include "base/threading/thread_task_runner_handle.h"
@@ skipping 72 matching lines @@
 
 void MemoryPressureMonitor::CheckMemoryPressureSoon() {
   DCHECK(thread_checker_.CalledOnValidThread());
 
   ThreadTaskRunnerHandle::Get()->PostTask(
       FROM_HERE, Bind(&MemoryPressureMonitor::CheckMemoryPressure,
                       weak_ptr_factory_.GetWeakPtr()));
 }
 
 MemoryPressureListener::MemoryPressureLevel
-MemoryPressureMonitor::GetCurrentPressureLevel() const {
+MemoryPressureMonitor::GetCurrentPressureLevel() {
   return current_memory_pressure_level_;
 }
 
 void MemoryPressureMonitor::InferThresholds() {
   // Default to a 'high' memory situation, which uses more conservative
   // thresholds.
   bool high_memory = true;
   MEMORYSTATUSEX mem_status = {};
   if (GetSystemMemoryStatus(&mem_status)) {
     static const DWORDLONG kLargeMemoryThresholdBytes =
@@ skipping 120 matching lines @@
   return true;
 }
 
 void MemoryPressureMonitor::SetDispatchCallback(
     const DispatchCallback& callback) {
   dispatch_callback_ = callback;
 }
 
 }  // namespace win
 }  // namespace base