Bug 1690746 - Migrate ARES6 - fix r=perftest-reviewers,Bebe

Please leave the landing to the author of the patch!
Latest build: https://treeherder.mozilla.org/#/jobs?repo=try&revision=e3aa1b7f74d905e8565b4afb2f62dc7b984381da

Differential Revision: https://phabricator.services.mozilla.com/D106929

third_party/webkit/PerformanceTests/ARES-6/driver.js

@@ -248,6 +248,7 @@ class Driver {
             var _data = ['raptor-benchmark', 'ares6', measuredValuesByFullName];
             console.log('ares6 source is about to post results to the raptor webext');
             window.postMessage(_data, '*');
+            window.sessionStorage.setItem('benchmark_results',  JSON.stringify(_data));
         }
 
     }