Adding Baseframework of the ResourceManager (all hooks and observers) are being put in place with a…

athena/resource_manager/memory_pressure_notifier.h

+// Copyright (c) 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 ATHENA_RESOURCE_MANAGER_MEMORY_PRESSURE_NOTIFIER_H_
+#define ATHENA_RESOURCE_MANAGER_MEMORY_PRESSURE_NOTIFIER_H_
+
+#include "base/memory/ref_counted.h"
+
+namespace athena {
+
+class MemoryPressureNotifierImpl;
+class ResourceManagerDelegate;
+
+////////////////////////////////////////////////////////////////////////////////
+// MemoryPressureObserver
+//
+// This observer gets informed once about a |MEMORY_PRESSURE_LOW|. When the
+// pressure exceeds, the observer will get polled until |MEMORY_PRESSURE_LOW| is
+// reached again to counter memory consumption.
+class MemoryPressureObserver {
+ public:
+  MemoryPressureObserver() {}
+  virtual ~MemoryPressureObserver() {}
+
+  // The reported memory pressure. Note: The value is intentionally abstracted
+  // since the real amount of free memory is only estimated (due to e.g. zram).
+  enum MemoryPressure {
+    MEMORY_PRESSURE_UNKNOWN,   // The memory pressure cannot be determined.
+    MEMORY_PRESSURE_LOW,       // Single call if memory fill level is below 50%.
+    MEMORY_PRESSURE_MODERATE,  // Polled for memory fill level of ~50 .. 75%.
+    MEMORY_PRESSURE_HIGH,      // Polled for memory fill level of ~75% .. 90%.
+    MEMORY_PRESSURE_CRITICAL,  // Polled for memory fill level of above ~90%.
+  };
+  // The observer.
+  virtual void OnMemoryPressure(MemoryPressure pressure) = 0;
+
+  // OS system interface functions. The delegate remains owned by the Observer.
+  virtual ResourceManagerDelegate* GetDelegate() = 0;
+};
+
+
+////////////////////////////////////////////////////////////////////////////////
+// MemoryPressureNotifier
+//
+// Class to handle the observation of our free memory. It notifies the owner of
+// memory fill level changes, so that it can take action to reduce memory by
+// reducing active activities.
+//
+// The observer will use 3 different fill levels: 50% full, 75% full and 90%
+// full.
+//
+// This object starts and stops the observation, and can be created or deleted
+// from any thread, but the observation occurs on the FILE thread, and the
+// owner gets notified through a UI thread call.
+class MemoryPressureNotifier {
+ public:
+  // The creator gets the |listener| object. Note that the ownership of the
+  // listener object remains with the creator.
+  explicit MemoryPressureNotifier(MemoryPressureObserver* listener);
+  ~MemoryPressureNotifier();
+
+ private:
+  scoped_refptr<MemoryPressureNotifierImpl> observer_;
+
+  DISALLOW_COPY_AND_ASSIGN(MemoryPressureNotifier);
+};
+
+}  // namespace athena
+
+#endif  // ATHENA_RESOURCE_MANAGER_MEMORY_PRESSURE_NOTIFIER_H_