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

athena/resource_manager/memory_pressure_notifier.cc

+// 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.
+
+#include "athena/resource_manager/memory_pressure_notifier.h"
+
+#include "athena/resource_manager/public/resource_manager_delegate.h"
+#include "base/time/time.h"
+
+
+namespace athena {
+
+MemoryPressureNotifier::MemoryPressureNotifier(
+    MemoryPressureObserver* listener)
+      : listener_(listener),
+        current_pressure_(MemoryPressureObserver::MEMORY_PRESSURE_UNKNOWN) {
+  StartObserving();
+}
+
+MemoryPressureNotifier::~MemoryPressureNotifier() {
+  StopObserving();
+}
+
+void MemoryPressureNotifier::StartObserving() {
+  int time_in_ms = listener_->GetDelegate()->MemoryPressureIntervalInMS();
+  timer_.Start(FROM_HERE,
+               base::TimeDelta::FromMilliseconds(time_in_ms),
+               base::Bind(&MemoryPressureNotifier::CheckMemoryPressure,
+                          base::Unretained(this)));
+}
+
+void MemoryPressureNotifier::StopObserving() {
+  // If StartObserving failed, StopObserving will still get called.
+  timer_.Stop();
+}
+
+void MemoryPressureNotifier::CheckMemoryPressure() {
+  MemoryPressureObserver::MemoryPressure pressure =
+      GetMemoryPressureLevelFromFillLevel(
+          listener_->GetDelegate()->GetUsedMemoryInPercent());
+  if (current_pressure_ != pressure ||
+      (pressure != MemoryPressureObserver::MEMORY_PRESSURE_LOW &&
+       pressure != MemoryPressureObserver::MEMORY_PRESSURE_UNKNOWN)) {
+    // If we are anything worse than |MEMORY_PRESSURE_LOW|, we notify the
+    // listener.
+    current_pressure_ = pressure;
+    listener_->OnMemoryPressure(current_pressure_);
+  }
+}
+
+MemoryPressureObserver::MemoryPressure
+MemoryPressureNotifier::GetMemoryPressureLevelFromFillLevel(
+    int memory_fill_level) {
+  if (memory_fill_level == 0)
+    return MemoryPressureObserver::MEMORY_PRESSURE_UNKNOWN;
+  if (memory_fill_level < 50)
+    return MemoryPressureObserver::MEMORY_PRESSURE_LOW;
+  if (memory_fill_level < 75)
+    return MemoryPressureObserver::MEMORY_PRESSURE_MODERATE;
+  if (memory_fill_level < 90)
+    return MemoryPressureObserver::MEMORY_PRESSURE_HIGH;
+  return MemoryPressureObserver::MEMORY_PRESSURE_CRITICAL;
+}
+
+}  // namespace athena