Add memory ablation experiment.

chrome/browser/experiments/memory_ablation_experiment.cc

+// Copyright 2017 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 "chrome/browser/experiments/memory_ablation_experiment.h"
+
+#include "base/bind.h"
+#include "base/bind_helpers.h"
+#include "base/debug/alias.h"
+#include "base/metrics/field_trial_params.h"
+#include "base/process/process_metrics.h"
+#include "base/sequenced_task_runner.h"
+
+const base::Feature kMemoryAblationFeature{"MemoryAblation",
+                                           base::FEATURE_DISABLED_BY_DEFAULT};
+
+const char kMemoryAblationFeatureSizeParam[] = "Size";
+
+constexpr size_t kMemoryAblationDelaySeconds = 5;
+
+MemoryAblationExperiment::MemoryAblationExperiment() {}
+
+MemoryAblationExperiment::~MemoryAblationExperiment() {}
+
+MemoryAblationExperiment* MemoryAblationExperiment::GetInstance() {
+  static auto* instance = new MemoryAblationExperiment();
+  return instance;
+}
+
+void MemoryAblationExperiment::MaybeStart(
+    scoped_refptr<base::SequencedTaskRunner> task_runner) {
+  int size = base::GetFieldTrialParamByFeatureAsInt(
+      kMemoryAblationFeature, kMemoryAblationFeatureSizeParam,
+      0 /* default value */);
+  if (size > 0) {
+    GetInstance()->Start(task_runner, size);
+  }
+}
+
+void MemoryAblationExperiment::Start(
+    scoped_refptr<base::SequencedTaskRunner> task_runner,
+    size_t memory_size) {
+  task_runner->PostDelayedTask(
+      FROM_HERE,
+      base::Bind(&MemoryAblationExperiment::AllocateMemory,
+                 base::Unretained(this), memory_size),
+      base::TimeDelta::FromSeconds(kMemoryAblationDelaySeconds));
+}
+
+void MemoryAblationExperiment::AllocateMemory(size_t size) {
+  memory_size_ = size;
+  memory_.reset(new uint8_t[size]);
+  TouchMemory();
+}
+
+void MemoryAblationExperiment::TouchMemory() {
+  if (memory_) {
+    size_t page_size = base::GetPageSize();
+    auto* memory = static_cast<volatile uint8_t*>(memory_.get());
+    for (size_t i = 0; i < memory_size_; i += page_size) {
+      memory[i] = i;
+    }
+    base::debug::Alias(memory_.get());
+  }
+}