metrics: Add leak detector controller in Chrome OS metrics system

components/metrics/leak_detector/leak_detector.h

Index: components/metrics/leak_detector/leak_detector.h
diff --git a/components/metrics/leak_detector/leak_detector.h b/components/metrics/leak_detector/leak_detector.h
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index 0000000000000000000000000000000000000000..da3f5d1fe3fdb05af17df4112ddf73f2f657fbfc
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+++ b/components/metrics/leak_detector/leak_detector.h
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+// 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"
+#include "base/observer_list.h"
+
+namespace metrics {
+
+// LeakDetector is an interface layer that connects the allocator
+// (base::allocator), the leak detector logic (LeakDetectorImpl), and any
+// external classes interested in receiving leak reports (extend the Observer
+// class).
+//
+// 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.
+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;
+  };
+
+  // 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);
+
+  // Initialize with default parameters.
+  LeakDetector();
+
+  ~LeakDetector();
+
+  // Add |observer| to the list of stored Observers, i.e. |observers_|, to which
+  // the leak detector will report leaks.
+  void AddObserver(Observer* observer);
+
+  // Remove |observer| from |observers_|.
+  void RemoveObserver(Observer* observer);
+
+  // Notifies all Observers in |observers_| with the given vector of leak
+  // reports.
+  void NotifyObservers(const std::vector<LeakReport>& reports);

[Alexei Svitkine (slow), 2016/02/12 16:17:42]

Does this need to be public? Kind of strange to have any public caller be able
to notify all the observers.

[Simon Que, 2016/02/12 19:00:07]

This will be called from the memory allocator hook function, which cannot be a
non-static class member. Either the hook func will have to be a static member of
this class, or this class will have to expose some interface to call this
function See here:
https://codereview.chromium.org/1665553002/diff/60001/components/metrics/leak...

[Alexei Svitkine (slow), 2016/02/17 16:06:30]

If having the hook be a static member of the class will work, then let's do
that.

However, how do you plan to for the hook to get at the LeakDetector instance to
call this on?

Regardless, I think it's fine to make it private for now and possibly move it in
the follow-up CL that adds the hook if necessary.

[Simon Que, 2016/02/17 20:49:33]

Done.

+
+ private:
+  // List of observers to notify when there's a leak report.
+  base::ObserverList<Observer> observers_;
+
+  DISALLOW_COPY_AND_ASSIGN(LeakDetector);
+};
+
+}  // namespace metrics
+
+#endif  // COMPONENTS_METRICS_LEAK_DETECTOR_LEAK_DETECTOR_H_