[MemoryPressure] Move chrome/browser/chromeos/* to chrome/browser/memory/*.

chrome/browser/chromeos/memory/low_memory_observer.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_LOW_MEMORY_OBSERVER_H_
-#define CHROME_BROWSER_CHROMEOS_MEMORY_LOW_MEMORY_OBSERVER_H_
-
-#include "base/memory/ref_counted.h"
-
-namespace chromeos {
-
-class LowMemoryObserverImpl;
-
-////////////////////////////////////////////////////////////////////////////////
-// LowMemoryObserver
-//
-// Class to handle observation of low memory device for changes so that we
-// can get a signal from the kernel about low memory conditions and discard tabs
-// when that happens, instead of waiting for the OOM killer to kill renderers
-// (which is more drastic, but still necessary and possible).
-//
-// 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 tabs are
-// discarded on the UI thread.
-class LowMemoryObserver {
- public:
-  LowMemoryObserver();
-  ~LowMemoryObserver();
-
-  void Start();
-  void Stop();
-
- private:
-  scoped_refptr<LowMemoryObserverImpl> observer_;
-
-  DISALLOW_COPY_AND_ASSIGN(LowMemoryObserver);
-};
-
-}  // namespace chromeos
-
-#endif  // CHROME_BROWSER_CHROMEOS_MEMORY_LOW_MEMORY_OBSERVER_H_