Remove memory_pressure component.

components/memory_pressure/memory_pressure_calculator.h

-// 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.
-
-#ifndef COMPONENTS_MEMORY_PRESSURE_MEMORY_PRESSURE_CALCULATOR_H_
-#define COMPONENTS_MEMORY_PRESSURE_MEMORY_PRESSURE_CALCULATOR_H_
-
-#include "base/macros.h"
-#include "components/memory_pressure/memory_pressure_listener.h"
-
-namespace memory_pressure {
-
-#if defined(MEMORY_PRESSURE_IS_POLLING)
-
-// Interface for a utility class that calculates memory pressure. Only used on
-// platforms without native memory pressure signals.
-class MemoryPressureCalculator {
- public:
-  using MemoryPressureLevel = MemoryPressureListener::MemoryPressureLevel;
-
-  MemoryPressureCalculator() {}
-  virtual ~MemoryPressureCalculator() {}
-  virtual MemoryPressureLevel CalculateCurrentPressureLevel() = 0;
-
- private:
-  DISALLOW_COPY_AND_ASSIGN(MemoryPressureCalculator);
-};
-
-#endif  // defined(MEMORY_PRESSURE_IS_POLLING)
-
-}  // namespace memory_pressure
-
-#endif  // COMPONENTS_MEMORY_PRESSURE_MEMORY_PRESSURE_CALCULATOR_H_