Using the new MemoryPressureListener instead of the LowMemoryObserver when the enhanced memory mana…

base/chromeos/memory_pressure_observer_chromeos.h

 // Copyright 2014 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_CHROMEOS_MEMORY_PRESSURE_OBSERVER_CHROMEOS_H_
 #define BASE_CHROMEOS_MEMORY_PRESSURE_OBSERVER_CHROMEOS_H_
 
 #include "base/base_export.h"
+#include "base/gtest_prod_util.h"
 #include "base/macros.h"
 #include "base/memory/memory_pressure_listener.h"
+#include "base/memory/weak_ptr.h"
 #include "base/timer/timer.h"
 
 namespace base {
 
+class TestMemoryPressureObserver;
+
 ////////////////////////////////////////////////////////////////////////////////
 // MemoryPressureObserverChromeOS
 //
 // A class to handle the observation of our free memory. It notifies the
 // MemoryPressureListener of memory fill level changes, so that it can take
 // action to reduce memory resources accordingly.
 //
 class BASE_EXPORT MemoryPressureObserverChromeOS {
  public:
+  using GetUsedMemoryInPercentCallback = int (*)();
+
   MemoryPressureObserverChromeOS();
-  ~MemoryPressureObserverChromeOS();
+  virtual ~MemoryPressureObserverChromeOS();
+
+  // Redo the memory pressure calculation soon and call again if a critical
+  // memory pressure prevails. Note that this call will trigger an asynchronous
+  // action which gives the system time to release memory back into the pool.
+  void ScheduleEarlyCheck();
 
   // Get the current memory pressure level.
   base::MemoryPressureListener::MemoryPressureLevel GetCurrentPressureLevel() {
     return current_memory_pressure_level_;
   }
 
  private:
+  friend TestMemoryPressureObserver;
   // Starts observing the memory fill level.
   // Calls to StartObserving should always be matched with calls to
   // StopObserving.
   void StartObserving();
 
   // Stop observing the memory fill level.
   // May be safely called if StartObserving has not been called.
   void StopObserving();
 
-  // The function which gets periodically be called to check any changes in the
-  // memory pressure.
+  // The function which gets periodically called to check any changes in the
+  // memory pressure. It will report pressure changes as well as continuous
+  // critical pressure levels.
   void CheckMemoryPressure();
 
+  // Get the memory pressure in percent (virtual for testing).
+  virtual int GetUsedMemoryInPercent();
+
   // The current memory pressure.
   base::MemoryPressureListener::MemoryPressureLevel
       current_memory_pressure_level_;
 
   // A periodic timer to check for resource pressure changes. This will get
   // replaced by a kernel triggered event system (see crbug.com/381196).
   base::RepeatingTimer<MemoryPressureObserverChromeOS> timer_;
 
+  // To slow down the amount of moderate pressure event calls, this counter
+  // gets used to count the number of events since the last event occured.
+  int moderate_pressure_repeat_count_;
+
+  base::WeakPtrFactory<MemoryPressureObserverChromeOS> weak_ptr_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(MemoryPressureObserverChromeOS);
 };
 
 }  // namespace base
 
 #endif  // BASE_CHROMEOS_MEMORY_PRESSURE_OBSERVER_CHROMEOS_H_