metrics: Add leak detector controller in Chrome OS metrics system

components/metrics/leak_detector/leak_detector.h

+// 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.
+
+#ifndef COMPONENTS_METRICS_LEAK_DETECTOR_LEAK_DETECTOR_H_
+#define COMPONENTS_METRICS_LEAK_DETECTOR_LEAK_DETECTOR_H_
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include <list>
+#include <vector>
+
+#include "base/macros.h"
+
+// The top level leak detector is an interface layer that connects the allocator

[Alexei Svitkine (slow), 2016/02/10 20:16:58]

I don't understand what "top level" means in this case. How about just
"LeakDetector is an interface layer that .."

[Simon Que, 2016/02/11 01:45:38]

Done.

+// the leak detector logic, and the leak reporting pipeline.
+//
+// Currently it is stubbed out and only provides an interface for registering
+// observers to receive leak reports.
+// TODO(sque): Add the full functionality and allow only one instance.

[Alexei Svitkine (slow), 2016/02/10 20:16:58]

Nit: Put this whole comment above the class declaration.

[Simon Que, 2016/02/11 01:45:38]

Done.

+
+namespace metrics {
+
+class LeakDetector {
+ public:
+  // Contains a report of a detected memory leak.
+  struct LeakReport {
+    LeakReport();
+    ~LeakReport();
+
+    size_t alloc_size_bytes;
+
+    // Unlike the CallStack struct, which consists of addresses, this call stack
+    // will contain offsets in the executable binary.
+    std::vector<uintptr_t> call_stack;
+
+    bool operator<(const LeakReport& other) const {

[Alexei Svitkine (slow), 2016/02/10 20:16:58]

Why is this needed?

[Simon Que, 2016/02/11 01:45:37]

It's used in the unit test. I've moved it to there.

+      if (alloc_size_bytes != other.alloc_size_bytes)
+        return alloc_size_bytes < other.alloc_size_bytes;
+
+      return call_stack < other.call_stack;
+    }
+  };
+
+  // Interface for receiving leak reports.
+  class Observer {
+   public:
+    virtual ~Observer() {}
+
+    // Called by leak detector to report a leak.
+    virtual void OnLeakFound(const LeakReport& report) = 0;
+  };
+
+  // Constructor arguments:
+  // sampling_rate:
+  //     Pseudorandomly sample a fraction of the incoming allocations and frees,
+  //     based on hash values. Setting to 0 means no allocs/frees are sampled.
+  //     Setting to 1.0 or more means all allocs/frees are sampled. Anything in
+  //     between will result in an approximately that fraction of allocs/frees
+  //     being sampled.
+  // max_stack_depth:
+  //     The max number of call stack frames to unwind.
+  // analysis_interval_bytes:
+  //     Perform a leak analysis each time this many bytes have been allocated
+  //     since the previous analysis.
+  // size_suspicion_threshold, call_stack_suspicion_threshold:
+  //     A possible leak should be suspected this many times to take action on i
+  //     For size analysis, the action is to start profiling by call stack.
+  //     For call stack analysis, the action is to generate a leak report.
+  LeakDetector(float sampling_rate,
+               int max_stack_depth,
+               uint64_t analysis_interval_bytes,
+               int size_suspicion_threshold,
+               int call_stack_suspicion_threshold);
+
+  ~LeakDetector();
+
+  // Add |observer| to the list of stored LeakDetectorObservers to which the
+  // leak detector will report leaks. Returns true on success.
+  bool AddObserver(Observer* observer);
+
+  // Remove |observer| from the list of stored LeakDetectorObservers. If it is
+  // not in the list, this function has no effect but returns false. Returns
+  // true on success.
+  bool RemoveObserver(Observer* observer);
+
+  // Notifies all Observers in |observers_| with the given vector of leak
+  // reports.
+  void NotifyObservers(const std::vector<LeakReport>& reports);
+
+ private:
+  // List of observers to notify when there's a leak report.
+  std::list<Observer*> observers_;

[Alexei Svitkine (slow), 2016/02/10 20:16:58]

Consider using base/observer_list.h

[Simon Que, 2016/02/11 01:45:38]

Done.

+
+  DISALLOW_COPY_AND_ASSIGN(LeakDetector);
+};
+
+}  // namespace metrics
+
+#endif  // COMPONENTS_METRICS_LEAK_DETECTOR_LEAK_DETECTOR_H_