Add oom tab killing and the about:discards page on linux

base/memory/memory_pressure_monitor_linux.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.h"
 
 #include "base/metrics/histogram_macros.h"
 #include "base/process/process_metrics.h"
 #include "base/single_thread_task_runner.h"
 #include "base/thread_task_runner_handle.h"
 #include "base/time/time.h"
 
 namespace base {
 
 namespace {
 
 // The time between memory pressure checks. While under critical pressure, this
 // is also the timer to repeat cleanup attempts.
 const int kMemoryPressureIntervalMs = 1000;
 
 // The time which should pass between two moderate memory pressure calls.
 const int kModerateMemoryPressureCooldownMs = 10000;
 
 // Number of event polls before the next moderate pressure event can be sent.
 const int kModerateMemoryPressureCooldown =
     kModerateMemoryPressureCooldownMs / kMemoryPressureIntervalMs;
 
 // Threshold constants to emit pressure events.
 const int kNormalMemoryPressureModerateThresholdPercent = 60;
-const int kNormalMemoryPressureCriticalThresholdPercent = 95;
+const int kNormalMemoryPressureCriticalThresholdPercent = 90;
 
 // The possible state for memory pressure level. The values should be in line
 // with values in MemoryPressureListener::MemoryPressureLevel and should be
 // updated if more memory pressure levels are introduced.
 enum MemoryPressureLevelUMA {
   UMA_MEMORY_PRESSURE_LEVEL_NONE = 0,
   UMA_MEMORY_PRESSURE_LEVEL_MODERATE = 1,
   UMA_MEMORY_PRESSURE_LEVEL_CRITICAL = 2,
   // This must be the last value in the enum.
   UMA_MEMORY_PRESSURE_LEVEL_COUNT,
@@ skipping 119 matching lines @@
   int64 total_memory = info.total;
   int64 available_memory = info.free;
 
   DCHECK(available_memory < total_memory);
   int percentage = static_cast<int>(((total_memory - available_memory) * 100) /
                                     total_memory);
   return percentage;
 }
 
 }  // namespace base