A visibile to invisible state change will also release memory and should therefore wait as an unloa…

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 "athena/athena_export.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 10 matching lines @@
 // 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).
+  // Note: The bigger the index of the pressure level, the more resources are
+  // in use.
   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%.
+    MEMORY_PRESSURE_UNKNOWN = 0,   // The memory pressure cannot be determined.
+    MEMORY_PRESSURE_LOW,           // Single call if fill level is below 50%.
+    MEMORY_PRESSURE_MODERATE,      // Polled for fill level of ~50 .. 75%.
+    MEMORY_PRESSURE_HIGH,          // Polled for fill level of ~75% .. 90%.
+    MEMORY_PRESSURE_CRITICAL,      // Polled for 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;
 };
 
 
 ////////////////////////////////////////////////////////////////////////////////
@@ skipping 37 matching lines @@
 
   // Our current memory pressure.
   MemoryPressureObserver::MemoryPressure current_pressure_;
 
   DISALLOW_COPY_AND_ASSIGN(MemoryPressureNotifier);
 };
 
 }  // namespace athena
 
 #endif  // ATHENA_RESOURCE_MANAGER_MEMORY_PRESSURE_NOTIFIER_H_