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

chrome/browser/chromeos/memory/oom_priority_manager.h

 // Copyright (c) 2012 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_CHROMEOS_MEMORY_OOM_PRIORITY_MANAGER_H_
 #define CHROME_BROWSER_CHROMEOS_MEMORY_OOM_PRIORITY_MANAGER_H_
 
 #include <utility>
 #include <vector>
 
 #include "base/compiler_specific.h"
 #include "base/containers/hash_tables.h"
 #include "base/gtest_prod_util.h"
+#include "base/memory/memory_pressure_listener.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/process/process.h"
 #include "base/strings/string16.h"
 #include "base/synchronization/lock.h"
 #include "base/time/time.h"
 #include "base/timer/timer.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 
 class GURL;
@@ skipping 107 matching lines @@
 
   // Sets the score of the focused tab to the least value.
   void AdjustFocusedTabScoreOnFileThread();
 
   static bool CompareTabStats(TabStats first, TabStats second);
 
   virtual void Observe(int type,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) override;
 
+  // Called by the memory pressure listener when the memory pressure rises.
+  void OnMemoryPressure(
+      base::MemoryPressureListener::MemoryPressureLevel memory_pressure_level);
+
   base::RepeatingTimer<OomPriorityManager> timer_;
   base::OneShotTimer<OomPriorityManager> focus_tab_score_adjust_timer_;
   base::RepeatingTimer<OomPriorityManager> recent_tab_discard_timer_;
   content::NotificationRegistrar registrar_;
 
   // This lock is for |oom_score_map_| and |focused_tab_process_info_|.
   base::Lock oom_score_lock_;
   // Map maintaining the child process host id - oom_score mapping.
   typedef base::hash_map<int, int> ProcessScoreMap;
   ProcessScoreMap oom_score_map_;
   // Holds the focused tab's child process host id.
   ProcessInfo focused_tab_process_info_;
 
-  // Observer for the kernel low memory signal.  NULL if tab discarding is
-  // disabled.
+  // The old observer for the kernel low memory signal. This is NULL if

[James Cook, 2014/12/19 19:38:08]

nit: NULL -> null in comments

[Mr4D (OOO till 08-26), 2014/12/19 23:34:41]

Done.

+  // the new MemoryPressureListener is used.
+  // TODO(skuhne): Remove this when the enhanced memory observer is turned on
+  // by default.
   scoped_ptr<LowMemoryObserver> low_memory_observer_;
 
+  // A listener to global memory pressure events. This will be used if the
+  // memory pressure system was instantiated - otherwise the LowMemoryObserver
+  // will be used.
+  scoped_ptr<base::MemoryPressureListener> memory_pressure_listener_;
+
   // Wall-clock time when the priority manager started running.
   base::TimeTicks start_time_;
 
   // Wall-clock time of last tab discard during this browsing session, or 0 if
   // no discard has happened yet.
   base::TimeTicks last_discard_time_;
 
   // Wall-clock time of last priority adjustment, used to correct the above
   // times for discontinuities caused by suspend/resume.
   base::TimeTicks last_adjust_time_;
 
   // Number of times we have discarded a tab, for statistics.
   int discard_count_;
 
   // Whether a tab discard event has occurred during the last time interval,
   // used for statistics normalized by usage.
   bool recent_tab_discard_;
 
   DISALLOW_COPY_AND_ASSIGN(OomPriorityManager);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_MEMORY_OOM_PRIORITY_MANAGER_H_