Add memory ablation experiment.

chrome/browser/experiments/memory_ablation_experiment.h

+// 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.
+
+#ifndef CHROME_BROWSER_EXPERIMENTS_MEMORY_ABLATION_EXPERIMENT_H_
+#define CHROME_BROWSER_EXPERIMENTS_MEMORY_ABLATION_EXPERIMENT_H_
+
+#include <stdlib.h>
+
+#include <memory>
+
+#include "base/feature_list.h"
+#include "base/memory/ref_counted.h"
+#include "base/sequenced_task_runner.h"

[Primiano Tucci (use gerrit), 2017/04/10 18:05:04]

can just forward declare this

[DmitrySkiba, 2017/04/10 19:31:00]

Done.

+
+extern const base::Feature kMemoryAblationFeature;
+extern const char kMemoryAblationFeatureSizeParam[];
+
+/* When enabled, this experiment allocates a chunk of memory to study
+ * correlation between memory usage and performance metrics.
+ */
+class MemoryAblationExperiment {
+ public:
+  ~MemoryAblationExperiment();
+
+  // Starts the experiment if corresponding field trial is enabled
+  static void MaybeStart(scoped_refptr<base::SequencedTaskRunner> task_runner);
+
+ private:
+  MemoryAblationExperiment();
+
+  void Start(scoped_refptr<base::SequencedTaskRunner> task_runner, size_t size);
+
+  void AllocateMemory(size_t size);
+  void TouchMemory();
+
+  static MemoryAblationExperiment* GetInstance();
+
+  size_t memory_size_ = 0;
+  std::unique_ptr<uint8_t[], decltype(free)*> memory_;

[Primiano Tucci (use gerrit), 2017/04/10 18:05:04]

this one seems over-complicated for the need.
Can you just have a std::unique_ptr<uint8_t[]> and just initialize that as

memory_(new uint8_t[size]) ?

using new vs delete shouldn't make any difference vs malloc. If you do to avoid
large zero-initializaiton, memory shouldn'be initialize unless you do new
(uint8_t[size]().

[DmitrySkiba, 2017/04/10 19:31:00]

Done. 

+};
+
+#endif  // CHROME_BROWSER_EXPERIMENTS_MEMORY_ABLATION_EXPERIMENT_H_