Added memory pressure monitor for linux.

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 "base/memory/memory_pressure_monitor.h"
 
 #include <windows.h>
 
 #include "base/metrics/histogram_macros.h"
 #include "base/single_thread_task_runner.h"
 #include "base/thread_task_runner_handle.h"
 #include "base/time/time.h"
 
 namespace base {
-namespace win {
 
 namespace {
 
 static const DWORDLONG kMBBytes = 1024 * 1024;
 
 // Enumeration of UMA memory pressure levels. This needs to be kept in sync with
 // histograms.xml and the memory pressure levels defined in
 // MemoryPressureListener.
 enum MemoryPressureLevelUMA {
   UMA_MEMORY_PRESSURE_LEVEL_NONE = 0,
@@ skipping 62 matching lines @@
 }
 
 MemoryPressureMonitor::MemoryPressureMonitor(int moderate_threshold_mb,
                                              int critical_threshold_mb)
     : moderate_threshold_mb_(moderate_threshold_mb),
       critical_threshold_mb_(critical_threshold_mb),
       current_memory_pressure_level_(
           MemoryPressureListener::MEMORY_PRESSURE_LEVEL_NONE),
       moderate_pressure_repeat_count_(0),
       weak_ptr_factory_(this) {
+  DCHECK(!g_monitor);
+  g_monitor = this;
+
   DCHECK_GE(moderate_threshold_mb_, critical_threshold_mb_);
   DCHECK_LE(0, critical_threshold_mb_);
   StartObserving();
 }
 
 MemoryPressureMonitor::~MemoryPressureMonitor() {
+  DCHECK(g_monitor);
+  g_monitor = nullptr;
+
   StopObserving();
 }
 
 void MemoryPressureMonitor::CheckMemoryPressureSoon() {
   DCHECK(thread_checker_.CalledOnValidThread());
 
   ThreadTaskRunnerHandle::Get()->PostTask(
       FROM_HERE, Bind(&MemoryPressureMonitor::CheckMemoryPressure,
                       weak_ptr_factory_.GetWeakPtr()));
 }
@@ skipping 129 matching lines @@
 
 bool MemoryPressureMonitor::GetSystemMemoryStatus(
     MEMORYSTATUSEX* mem_status) {
   DCHECK(mem_status != nullptr);
   mem_status->dwLength = sizeof(*mem_status);
   if (!::GlobalMemoryStatusEx(mem_status))
     return false;
   return true;
 }
 
-}  // namespace win
 }  // namespace base