Support arbitrary timepoint granularity QuantileEstimations

Summary: This change should not make a functional difference to any existing callers. The underlying data structure stores a TimePoint.

Reviewed By: yfeldblum

Differential Revision: D34060591

fbshipit-source-id: b2b4d7f0d7fed8220cffb6b1dba5082d21073686

folly/stats/QuantileEstimator-inl.h

@@ -42,7 +42,7 @@ void SimpleQuantileEstimator<ClockT>::addValue(double value, TimePoint now) {
 
 template <typename ClockT>
 SlidingWindowQuantileEstimator<ClockT>::SlidingWindowQuantileEstimator(
-    std::chrono::seconds windowDuration, size_t nWindows)
+    Duration windowDuration, size_t nWindows)
     : bufferedSlidingWindow_(nWindows, windowDuration, 1000, 100) {}
 
 template <typename ClockT>

folly/stats/QuantileEstimator.h

@@ -65,9 +65,9 @@ template <typename ClockT = std::chrono::steady_clock>
 class SlidingWindowQuantileEstimator {
  public:
   using TimePoint = typename ClockT::time_point;
+  using Duration = typename ClockT::duration;
 
-  SlidingWindowQuantileEstimator(
-      std::chrono::seconds windowDuration, size_t nWindows = 60);
+  SlidingWindowQuantileEstimator(Duration windowDuration, size_t nWindows = 60);
 
   QuantileEstimates estimateQuantiles(
       Range<const double*> quantiles, TimePoint now = ClockT::now());