[Chromecast] Add free memory UMA histograms

chromecast/browser/cast_memory_pressure_monitor.cc

 // Copyright 2016 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 "chromecast/browser/cast_memory_pressure_monitor.h"
 
 #include <algorithm>
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/location.h"
+#include "base/metrics/histogram_macros.h"
 #include "base/process/process_metrics.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "chromecast/base/chromecast_switches.h"
 #include "chromecast/base/metrics/cast_metrics_helper.h"
 
 namespace chromecast {
 namespace {
 
 // Memory thresholds (as fraction of total memory) for memory pressure levels.
@@ skipping 59 matching lines @@
       DCHECK(total > 0);
 
       if ((max_free / total) < kCriticalMemoryFraction)
         level = base::MemoryPressureListener::MEMORY_PRESSURE_LEVEL_CRITICAL;
       else if ((max_free / total) < kModerateMemoryFraction)
         level = base::MemoryPressureListener::MEMORY_PRESSURE_LEVEL_MODERATE;
     }
   }
 
   UpdateMemoryPressureLevel(level);
+
+  UMA_HISTOGRAM_PERCENTAGE("Platform.MeminfoMemFree",
+                           (info.free * 100.0) / info.total);
+  UMA_HISTOGRAM_CUSTOM_COUNTS("Platform.MeminfoMemFreeDerived",
+                              info.free + info.buffers + info.cached, 1,
+                              info.total, 100);

[wzhong, 2016/06/01 20:24:25]

The info.total varies by platform though, for example can be 2G on TV product.

+
   base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
       FROM_HERE, base::Bind(&CastMemoryPressureMonitor::PollPressureLevel,
                             weak_ptr_factory_.GetWeakPtr()),
       base::TimeDelta::FromMilliseconds(kPollingIntervalMS));
 }
 
 void CastMemoryPressureMonitor::UpdateMemoryPressureLevel(
     MemoryPressureLevel new_level) {
   if (new_level != base::MemoryPressureListener::MEMORY_PRESSURE_LEVEL_NONE)
     base::MemoryPressureListener::NotifyMemoryPressure(new_level);
 
   if (new_level == current_level_)
     return;
 
   current_level_ = new_level;
   metrics::CastMetricsHelper::GetInstance()->RecordApplicationEventWithValue(
       "Memory.Pressure.LevelChange", new_level);
 }
 
 }  // namespace chromecast