Add MemoryPurgeController

Source/platform/MemoryPurgeController.cpp

+// Copyright 2015 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 "config.h"
+#include "platform/MemoryPurgeController.h"
+
+#include "public/platform/Platform.h"
+
+namespace blink {
+
+MemoryPurgeController::MemoryPurgeController()
+    : m_deviceKind(Platform::current()->isLowEndDeviceMode() ? LowEnd : NotSpecified)
+{
+}
+
+void MemoryPurgeController::didBecomeInactive()
+{
+    purgeMemory(Inactive);
+}
+
+void MemoryPurgeController::purgeMemory(MemoryPurgeMode purgeMode)
+{
+    for (auto& listener : m_listeners)
+        listener->purgeMemory(purgeMode, m_deviceKind);
+}
+
+} // namespace blink