/**
 * Sets the start time.
 *
 * @param   double  $startTime  Unix timestamp in microseconds for setting the Profiler start time.
 * @param   int     $startMem   Memory amount in bytes for setting the Profiler start memory.
 *
 * @return  $this   For chaining
 *
 * @since   3.0.0
 */
public function setStart($startTime = 0.0, $startMem = 0)
{
    $this->start = (double) $startTime;
    $this->previousMem = (int) $startMem / 1048576;
    return $this;
}