Make memory pressure notifier configurable

base/memory/memory_pressure_monitor_win.h

Index: base/memory/memory_pressure_monitor_win.h
diff --git a/base/memory/memory_pressure_monitor_win.h b/base/memory/memory_pressure_monitor_win.h
index 5689ac6ac74a2befa9f2fac5d749948562953437..2d7838ccb6ca7ce58d5a028c905662de4feaa792 100644
--- a/base/memory/memory_pressure_monitor_win.h
+++ b/base/memory/memory_pressure_monitor_win.h
@@ -111,7 +111,9 @@ class BASE_EXPORT MemoryPressureMonitor : public base::MemoryPressureMonitor {
   // thread.
   virtual bool GetSystemMemoryStatus(MEMORYSTATUSEX* mem_status);
 
- private:
+  void SetDispatchCallback(DispatchCallback callback) override;
+
+private:
   // 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_;
@@ -132,6 +134,9 @@ class BASE_EXPORT MemoryPressureMonitor : public base::MemoryPressureMonitor {
   // Ensures that this object is used from a single thread.
   base::ThreadChecker thread_checker_;
 
+  DispatchCallback dispatch_callback_ =
+      &MemoryPressureListener::NotifyMemoryPressure;
+
   // Weak pointer factory to ourself used for scheduling calls to
   // CheckMemoryPressure/CheckMemoryPressureAndRecordStatistics via |timer_|.
   base::WeakPtrFactory<MemoryPressureMonitor> weak_ptr_factory_;