Revert of Added GetCpuTime to base/ to get total CPU time consumed by process for perf tests.

webrtc/base/cpu_time.h

-/*
- *  Copyright (c) 2017 The WebRTC project authors. All Rights Reserved.
- *
- *  Use of this source code is governed by a BSD-style license
- *  that can be found in the LICENSE file in the root of the source
- *  tree. An additional intellectual property rights grant can be found
- *  in the file PATENTS.  All contributing project authors may
- *  be found in the AUTHORS file in the root of the source tree.
- */
-
-#ifndef WEBRTC_BASE_CPU_TIME_H_
-#define WEBRTC_BASE_CPU_TIME_H_
-
-#include <stdint.h>
-
-namespace rtc {
-
-// Returns total CPU time of a current process in nanoseconds.
-// Time base is unknown, therefore use only to calculate deltas.
-int64_t GetProcessCpuTimeNanos();
-
-// Returns total CPU time of a current thread in nanoseconds.
-// Time base is unknown, therefore use only to calculate deltas.
-int64_t GetThreadCpuTimeNanos();
-
-}  // namespace rtc
-
-#endif  // WEBRTC_BASE_CPU_TIME_H_