Add Mac memory pressure statistic reporting and consolidate platform code

base/memory/memory_pressure_monitor_chromeos.cc

 // Copyright 2014 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_chromeos.h"
 
 #include <fcntl.h>
 #include <sys/select.h>
 
 #include "base/metrics/histogram_macros.h"
@@ skipping 90 matching lines @@
   return HANDLE_EINTR(select(file_descriptor + 1, &fds, NULL, NULL, &tv)) > 0;
 }
 
 }  // namespace
 
 MemoryPressureMonitor::MemoryPressureMonitor(
     MemoryPressureThresholds thresholds)
     : current_memory_pressure_level_(
           MemoryPressureListener::MEMORY_PRESSURE_LEVEL_NONE),
       moderate_pressure_repeat_count_(0),
+      seconds_since_reporting_(0),
       moderate_pressure_threshold_percent_(
           GetModerateMemoryThresholdInPercent(thresholds)),
       critical_pressure_threshold_percent_(
           GetCriticalMemoryThresholdInPercent(thresholds)),
       low_mem_file_(HANDLE_EINTR(::open(kLowMemFile, O_RDONLY))),
       dispatch_callback_(
           base::Bind(&MemoryPressureListener::NotifyMemoryPressure)),
       weak_ptr_factory_(this) {
   StartObserving();
   LOG_IF(ERROR,
@@ skipping 30 matching lines @@
                     weak_ptr_factory_.GetWeakPtr()));
 }
 
 void MemoryPressureMonitor::StopObserving() {
   // If StartObserving failed, StopObserving will still get called.
   timer_.Stop();
 }
 
 void MemoryPressureMonitor::CheckMemoryPressureAndRecordStatistics() {
   CheckMemoryPressure();
-
+  if (seconds_since_reporting_++ == 5) {
+    seconds_since_reporting_ = 0;
+    RecordMemoryPressure(current_memory_pressure_level_, 1);
+  }
   // Record UMA histogram statistics for the current memory pressure level.
+  // TODO(lgrey): Remove this once there's a usable history for the
+  // "Memory.PressureLevel" statistic
   MemoryPressureLevelUMA memory_pressure_level_uma(MEMORY_PRESSURE_LEVEL_NONE);
   switch (current_memory_pressure_level_) {
     case MemoryPressureListener::MEMORY_PRESSURE_LEVEL_NONE:
       memory_pressure_level_uma = MEMORY_PRESSURE_LEVEL_NONE;
       break;
     case MemoryPressureListener::MEMORY_PRESSURE_LEVEL_MODERATE:
       memory_pressure_level_uma = MEMORY_PRESSURE_LEVEL_MODERATE;
       break;
     case MemoryPressureListener::MEMORY_PRESSURE_LEVEL_CRITICAL:
       memory_pressure_level_uma = MEMORY_PRESSURE_LEVEL_CRITICAL;
@@ skipping 100 matching lines @@
   return percentage;
 }
 
 void MemoryPressureMonitor::SetDispatchCallback(
     const DispatchCallback& callback) {
   dispatch_callback_ = callback;
 }
 
 }  // namespace chromeos
 }  // namespace base