[fixup] Add comments

src/OrbitGl/MultivariateTimeSeries.h

@@ -77,6 +77,13 @@ class MultivariateTimeSeries {
     TimeSeriesEntryIter begin;
     TimeSeriesEntryIter end;
   };
+  // If there is no overlap between time range [min_time, max_time] and [StartTimeInNs(),
+  // EndTimeInNs()], return std::nullopt. Otherwise return a range of entries affected by the time
+  // range [min_time, max_time] where:
+  // * `Range::begin` points to the entry with the time key right before the time range (min_time,
+  // max_time) if exists; otherwise points to the fist entry.
+  // * `Range::end` points to the entry with the time key right after the time range (min_time,
+  // max_time) if exists; otherwise points to the last entry.
   [[nodiscard]] std::optional<Range> GetEntriesAffectedByTimeRange(uint64_t min_time,
                                                                    uint64_t max_time) const {
     if (IsEmpty() || min_time >= max_time || min_time >= time_to_series_values_.rbegin()->first ||