Make memory pressure notifier configurable

base/memory/memory_pressure_monitor_win.h

 // Copyright 2015 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 BASE_MEMORY_MEMORY_PRESSURE_MONITOR_WIN_H_
 #define BASE_MEMORY_MEMORY_PRESSURE_MONITOR_WIN_H_
 
 #include "base/base_export.h"
 #include "base/macros.h"
 #include "base/memory/memory_pressure_listener.h"
@@ skipping 52 matching lines @@
 
   // Get the current memory pressure level. This can be called from any thread.
   MemoryPressureLevel GetCurrentPressureLevel() const override;
 
   // Returns the moderate pressure level free memory threshold, in MB.
   int moderate_threshold_mb() const { return moderate_threshold_mb_; }
 
   // Returns the critical pressure level free memory threshold, in MB.
   int critical_threshold_mb() const { return critical_threshold_mb_; }
 
+  void SetObserver(MemoryPressureMonitorObserver* observer) override;
+
  protected:
   // Internals are exposed for unittests.
 
   // Automatically infers threshold values based on system memory. This invokes
   // GetMemoryStatus so it can be mocked in unittests.
   void InferThresholds();
 
   // Starts observing the memory fill level. Calls to StartObserving should
   // always be matched with calls to StopObserving.
   void StartObserving();
@@ skipping 22 matching lines @@
   // use any hysteresis and simply returns the result at the current moment. Can
   // be called on any thread.
   MemoryPressureLevel CalculateCurrentPressureLevel();
 
   // Gets system memory status. This is virtual as a unittesting hook. Returns
   // true if the system call succeeds, false otherwise. Can be called on any
   // thread.
   virtual bool GetSystemMemoryStatus(MEMORYSTATUSEX* mem_status);
 
  private:
+  void Notify(MemoryPressureLevel level);
+
   // Threshold amounts of available memory that trigger pressure levels. See
   // memory_pressure_monitor.cc for a discussion of reasonable values for these.
   int moderate_threshold_mb_;
   int critical_threshold_mb_;
 
   // A periodic timer to check for memory pressure changes.
   base::RepeatingTimer timer_;
 
   // The current memory pressure.
   MemoryPressureLevel current_memory_pressure_level_;
 
   // To slow down the amount of moderate pressure event calls, this gets used to
   // count the number of events since the last event occured. This is used by
   // |CheckMemoryPressure| to apply hysteresis on the raw results of
   // |CalculateCurrentPressureLevel|.
   int moderate_pressure_repeat_count_;
 
   // Ensures that this object is used from a single thread.
   base::ThreadChecker thread_checker_;
 
+  MemoryPressureMonitorObserver* observer_ = nullptr;
+
   // Weak pointer factory to ourself used for scheduling calls to
   // CheckMemoryPressure/CheckMemoryPressureAndRecordStatistics via |timer_|.
   base::WeakPtrFactory<MemoryPressureMonitor> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(MemoryPressureMonitor);
 };
 
 }  // namespace win
 }  // namespace base
 
 #endif  // BASE_MEMORY_MEMORY_PRESSURE_MONITOR_WIN_H_