Create statDefs in-place.

Summary: not a big deal, but no need to copy defs if they can be created in-place

Reviewed By: dmm-fb

Differential Revision: D75710904

fbshipit-source-id: 9c9986f5db522092aa8f3c70bce0643f2dbe6824

Author: ttsugriy

fb303/ServiceData.cpp

@@ -238,15 +238,13 @@ std::shared_ptr<QuantileStat> ServiceData::getQuantileStat(
   std::vector<detail::QuantileStatMap::StatDef> statDefs;
   statDefs.reserve(stats.size() + quantiles.size());
   for (auto statType : stats) {
-    detail::QuantileStatMap::StatDef statDef;
+    auto& statDef = statDefs.emplace_back();
     statDef.type = statType;
-    statDefs.push_back(statDef);
   }
   for (auto quantile : quantiles) {
-    detail::QuantileStatMap::StatDef statDef;
+    auto& statDef = statDefs.emplace_back();
     statDef.type = ExportType::PERCENT;
     statDef.quantile = quantile;
-    statDefs.push_back(statDef);
   }
 
   return quantileMap_.registerQuantileStat(