Randomly enable leak detector based on probability parameter

chrome/browser/metrics/leak_detector/leak_detector_remote_controller.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 CHROME_BROWSER_METRICS_LEAK_DETECTOR_LEAK_DETECTOR_REMOTE_CONTROLLER_H_
 #define CHROME_BROWSER_METRICS_LEAK_DETECTOR_LEAK_DETECTOR_REMOTE_CONTROLLER_H_
 
 #include <string>
 #include <vector>
 
 #include "base/macros.h"
 #include "components/metrics/leak_detector/leak_detector.mojom.h"
 #include "components/metrics/proto/memory_leak_report.pb.h"
 #include "mojo/public/cpp/bindings/interface_request.h"
 #include "mojo/public/cpp/bindings/strong_binding.h"
 
 namespace metrics {
 
 // This class acts as an interface to LeakDetector clients running on processes
 // other than its own (the browser process).
 class LeakDetectorRemoteController : public mojom::LeakDetector {
  public:
   // Interface class to be implemented by a local controller class that provides
   // leak detector parameters and can pass leak reports to UMA.
   class LocalController {
    public:
     virtual ~LocalController() {}
 
     // Returns a set of leak detection params to be used when initializing the
-    // leak detector on a remote process.
-    virtual MemoryLeakReportProto::Params GetParams() const = 0;
+    // leak detector on a remote process. The controller may vary the parameters
+    // between each call to this function, and to change its internal state.
+    // Hence this is function is not const.
+    virtual MemoryLeakReportProto::Params GetParamsAndRecordRequest() = 0;
 
     // Pass a vector of memory leak reports provided by a remote process to the
     // local controller class.
     virtual void SendLeakReports(
         const std::vector<MemoryLeakReportProto>& reports) = 0;
 
     // Signal that a remote process that had been running the leak detector
     // (i.e. been given params with sampling_rate = 0).
     virtual void OnRemoteProcessShutdown() = 0;
   };
 
   ~LeakDetectorRemoteController() override;
 
   static void Create(mojom::LeakDetectorRequest request);
 
   // mojom::LeakDetector:
   void GetParams(
       const mojom::LeakDetector::GetParamsCallback& callback) override;
   void SendLeakReports(std::vector<mojom::MemoryLeakReportPtr>) override;
 
   // Sets a global pointer to a LocalController implementation. The global
   // pointer is defined in the .cc file.
   static void SetLocalControllerInstance(LocalController* controller);
 
  private:
   explicit LeakDetectorRemoteController(mojom::LeakDetectorRequest request);
 
+  // Gets called when the remote process terminates and the Mojo connection gets
+  // closed as a result.
+  void OnRemoteProcessShutdown();
+
   mojo::StrongBinding<mojom::LeakDetector> binding_;
 
+  // Indicates whether remote process received MemoryLeakReportProto::Params
+  // with a non-zero sampling rate, i.e. enabled leak detector.
+  bool leak_detector_enabled_on_remote_process_;
+
   DISALLOW_COPY_AND_ASSIGN(LeakDetectorRemoteController);
 };
 
 }  // namespace metrics
 
 #endif  // CHROME_BROWSER_METRICS_LEAK_DETECTOR_LEAK_DETECTOR_REMOTE_CONTROLLER_H_