code: public void startTiming(String label) {
          if (mPerfWriter != null)
              mPerfWriter.writeStartTiming(label);
          mPerfMeasurement = new Bundle();
          mPerfMeasurement.putParcelableArrayList(
                  METRIC_KEY_ITERATIONS, new ArrayList<Parcelable>());
          mExecTime = SystemClock.uptimeMillis();
          mCpuTime = Process.getElapsedCpuTime();
      }
docs: Start measurement of user and cpu time.
  
  @param label description of code block between startTiming and
  stopTiming, used to label output