Add percentiles to runtime perf data

Change-Id: I75dfadcddb4baed3ee1e78e9168f6eaa866226a6
diff --git a/tools/perf/utils.js b/tools/perf/utils.js
index 46890d0..13cd09c 100644
--- a/tools/perf/utils.js
+++ b/tools/perf/utils.js
@@ -15,11 +15,14 @@
   return resultsForIteration[resultName];
 }
 
-function getAllResults(benchmark, commit, resultName) {
+function getAllResults(benchmark, commit, resultName, transformation) {
   const result = [];
   const allResults = commit.benchmarks[benchmark].results;
   for (var iteration = 0; iteration < allResults.length; iteration++) {
     result.push(getSingleResult(benchmark, commit, resultName, iteration));
   }
+  if (transformation) {
+    return transformation(result);
+  }
   return result;
 }