[perf] Fix compile errors in MovingAverage.
[perf] Fix compile errors in MovingAverage.

mit-carbon/Graphite-Cycle-Level,8l/Graphite,8l/Graphite,victorisildur/Graphite,nkawahara/Graphite,mit-carbon/Graphite,8l/Graphite,mit-carbon/Graphite,mit-carbon/Graphite,victorisildur/Graphite,mit-carbon/Graphite-Cycle-Level,victorisildur/Graphite,nkawahara/Graphite,mit-carbon/Graphite,nkawahara/Graphite,fhijaz/Graphite,mit-carbon/Graphite-Cycle-Level,fhijaz/Graphite,nkawahara/Graphite,fhijaz/Graphite,fhijaz/Graphite,8l/Graphite,mit-carbon/Graphite-Cycle-Level,victorisildur/Graphite